Damien Richard

Alteration of Glutamate/GABA Balance During Acute Alcohol Withdrawal in Emergency Department: A Prospective Analysis

AIMS Animal studies suggest that in alcohol withdrawal the balance of neurotransmitters gamma aminobutyric acid (GABA) and glutamate is altered. To test this in humans, we aimed to measure plasma levels of glutamate, GABA and glutamate/GABA ratio in alcoholic patients presenting with complicated AWS with the same values in non-alcohol abuser/dependent controls and to determine prognostic factors for severe withdrawal. METHODS 88 patients admitted to the emergency room for acute alcohol intoxication (DSM-IV) were prospectively included. Measurements of GABA and glutamate were performed on admission (Time 1, T1) and after 12 ± 2 h (T2). The experimental group (EG) was composed of 23 patients who presented at T2 with a severe AWS. The control group (CG) consisted of healthy subjects paired with the EG (gender and age). Logistic regression was performed in order to compare associated clinical and biological variables that could predict severe withdrawal. RESULTS The concentration of GABA in the EG at T1 was significantly lower than that in the CG. The concentration of glutamate in the EG at T1 was significantly higher than that in the CG. The glutamate/GABA ratio in the EG at T1 was significantly higher than the ratio in the CG. With a multivariate logistic regression model, glutamate level at admission remained the only criterion identified as a predictor of AWS at 12 h. CONCLUSION Decreased synthesis of GABA and increased synthesis of glutamate might be related to withdrawal symptoms experienced on brutal cessation of chronic alcohol intake.

Fully automated semi-quantitative toxicological screening in three biological matrices using turbulent flow chromatography/high resolution mass spectrometry.

BACKGROUND In clinical and forensic toxicology, fast and specific methods are needed for the screening of different classes of drugs. A complete general unknown screening procedure was developed using turbulent flow chromatography with electrospray ionization and Orbitrap mass spectrometry. METHODS After protein precipitation, samples were injected directly into the turbulent flow chromatographic system and analyzed with an Orbitrap mass spectrometer. The Exactive® operated in positive and negative modes with alternated high collision dissociation in order to obtain characteristic fragments. We built a library containing 616 compounds by analyzing a reference standard for all the molecules. RESULTS Identification was based on retention time, accurate measured mass, isotopic pattern and presence of specific fragments. For each substance, we set a calibration range encompassing infra-therapeutic, therapeutic, supra-therapeutic and toxic concentrations in order to generate semi-quantitative result. For 65% of the components, the limit of detection was below 5 ng/mL. The validation process showed the approach to be selective, sensitive, accurate and precise. CONCLUSION The method has been accredited by COFRAC (French Accreditation Committee) according to the ISO 15189 standard. Applicability was successfully tested by analyzing authentic serum, urine and whole blood samples.

Determination of irinotecan and SN38 in human plasma by TurboFlow™ liquid chromatography-tandem mass spectrometry.

Irinotecan is a cytotoxic agent used in the treatment of metastatic colorectal cancer. Irinotecan is a prodrug when is converted in vivo to an active metabolite SN38, which has potent pharmacological activity. SN38 is then inactivated and excreted as SN38-glucuronide. High-performance liquid chromatography-mass spectrometry is a widely used bioanalysis technique that can be coupled to the turbulent-flow extraction line to shorten preparation time. A technique was developed to quantify irinotecan and its metabolite by liquid chromatography-tandem mass spectrometry coupled with a turbulent-flow online extraction method. Assays were performed on 100 μL of plasma after protein precipitation. The supernatant is injected directly into the extraction column, transferred to the chromatographic column, and analyzed by tandem mass spectrometry. Linearity, reproducibility and repeatability of the method were validated on a concentration range of 25-2500 ng/mL for irinotecan and 5-500 ng/mL for SN38. For the low limit of quantification of irinotecan and SN38, precision is 6.31% and 8.73%, and accuracy is 84.0% and 91.8%, respectively. The SN38-glucuronide determination protocol included a hydrolyzation step. This method was successfully used to quantify irinotecan, SN38 and SN38-G in human plasma in a clinical trial.

Increasing spinal 5-HT2A receptor responsiveness mediates anti-allodynic effect and potentiates Fluoxetine efficacy in neuropathic rats. Evidence for GABA release.

Graphical abstract Figure. No caption available. &NA; Antidepressants are one of the first line treatments for neuropathic pain but their use is limited by the incidence and severity of side effects of tricyclics and the weak effectiveness of selective serotonin reuptake inhibitors (SSRIs). Serotonin type 2A (5‐HT2A) receptors interact with PDZ proteins that regulate their functionality and SSRI efficacy to alleviate pain. We investigated whether an interfering peptide (TAT‐2ASCV) disrupting the interaction between 5‐HT2A receptors and associated PDZ proteins would improve the treatment of traumatic neuropathic allodynia. Tactile allodynia was assessed in spinal nerve ligation‐induced neuropathic pain in rats using von Frey filaments after acute treatment with TAT‐2ASCV and/or 5‐HT2A receptor agonist, alone or in combination with repeated treatment with fluoxetine. In vivo microdialysis was performed in order to examine the involvement of GABA in TAT‐2ASCV/fluoxetine treatment‐associated analgesia. TAT‐2ASCV (100 ng, single i.t. injection) improved SNL‐induced tactile allodynia by increasing 5‐HT2A receptor responsiveness to endogenous 5‐HT. Fluoxetine alone (10 mg/kg, five i.p. injections) slightly increased tactile thresholds and its co‐administration with TAT‐2ASCV (100 ng, single i.t. injection) further enhanced the anti‐allodynic effect. This effect depends on the integrity of descending serotonergic bulbospinal pathways and spinal release of GABA. The anti‐allodynic effect of fluoxetine can be enhanced by disrupting 5‐HT2A receptor‐PDZ protein interactions. This enhancement depends on 5‐HT2A receptor activation, spinal GABA release and GABAA receptor activation.

Absence of painful neuropathy after chronic oral fluoride intake in Sprague-Dawley and Lou/C rats.

The possibility that chronicle oral ingestion of fluoride-rich water could modify peripheral pain sensitivity was studied in two strains of adult rats, Sprague-Dawley and Lou/C rats. Sodium fluoride was given orally in water to male Sprague-Dawley (75 and 150 ppm) and Lou rats (150 ppm) for 15 and 27 weeks, respectively. Using classical behavioural evaluation methods of pain symptoms, only slight tendencies to a thermal hyperalgia and a mechanical allodynia were observed in Sprague-Dawley rats.

Quinine clearance during continuous veno-venous high-volume hemofiltration

Quinine is eliminated primarily via hepatic biotransformation and only 15–30% is urinary excreted. There is no standard recommended quinine dose in patients with severe malaria requiring renal replacement therapy. Data on quinine levels during renal replacement therapy in patients with acute renal failure are scarce [1–4]. Previous reports describing the pharmacokinetics of quinine during hemofiltration showed no impact of the technique on quinine levels [1, 2]. However, it is unknown whether increasing the ultrafiltrate flow rate has an impact on quinine clearance and therefore requires quinine dosage to be modified. To our knowledge this is the first report of quinine level monitoring in an anuric patient treated with continuous venovenous high volume hemofiltration (CVVHVHF). A 44-year-old man weighing 83 kg was admitted to the intensive care unit (ICU) for coma and shock due to severe imported falciparum malaria with an initial parasitemia of 25%. Quinine was continuously administered in intravenous mode (24 mg/kg/ day) after a 1300 mg-loading dose. The patient rapidly developed multiorgan failure with anuria, and CVVHVHF was initiated 30 h after ICU admission (Fig. 1). Venous access was achieved with two polyurethane single lumen dialysis catheters (Gamcath catheters, Gambro, Hechingen, Germany) placed side by side. A Diapact continuous renal replacement therapy machine (Braun, Melsungen, Germany) was used with a high-flux synthetic membrane, polyamide Polyflux 14S (Gambro SA), 1.4 m Kuf, 50 mL/h per mmHg. Blood and ultrafiltrate flows were 200 ml/min and 6 L/h, respectively. The replacement fluid (Hemosol B0, Biosol, Sondalo, Italy) was delivered before filtering. No change was made to the quinine regimen. Ultrafiltrate and plasma quinine levels were determined during CVVHVHF (Fig. 1) with a gas chromatography/ mass spectrometric method. Samples were obtained before the addition of the replacement fluid and after filtering. Extraction of both protein-bound and -unbound quinine was made with Oasis MCX cartridges. The mass spectrometry was run in Selected Ion Monitoring mode. Quantification and confirmation ions were m/z 136, 261 and 381. Quantification range was 40– 10,000 lg/L. Standard formulae were used for mass transfer and clearance calculations [5]. During CVVHVHF, no great variation in prefilter and postfilter plasma quinine levels, and in quinine mass transfer were observed over time, probably because of the relatively high volume of distribution (1.8 ± 0.4 L/kg), and high protein binding rate (85–90%) of quinine. Since the sieving coefficient was 0.04 ± 0.01 (range 0.02–0.05), despite a high ultrafiltrate flow rate, the value of quinine clearance remained low 3.7 ± 0.8 ml/min range (1.9–5.1). The results observed were similar during the three CVVHD sessions suggesting that the quinine pharmacokinetic observed in our patient may be extrapolated to other patients treated with CVVHVHF. One limitation of the study is the absence of concomitant determination of 3-hydroxyquinine, the main metabolite of the quinine, that accumulates in acute renal failure but that probably contributes relatively little to antimalarial activity or toxicity in the acute phase of the disease [4]. Our findings suggest the need to use a standard quinine dosage (and not a high one) to achieve therapeutic levels during CVVHVHF in severe anuric malaria. 0,1 1,0 10,0 100,0

Targeting the TREK-1 potassium channel via riluzole to eliminate the neuropathic and depressive-like effects of oxaliplatin

Abstract: Neurotoxicity remains the most common adverse effect of oxaliplatin, limiting its clinical use. In the present study, we developed a mouse model of chronic oxaliplatin‐induced neuropathy, which mimics both sensory and motor deficits observed in patients, in a clinically relevant time course. Repeated oxaliplatin administration in mice induced both cephalic and extracephalic long lasting mechanical and cold hypersensitivity after the first injection as well as delayed sensorimotor deficits and a depression‐like phenotype. Using this model, we report that riluzole prevents both sensory and motor deficits induced by oxaliplatin as well as the depression‐like phenotype induced by cumulative chemotherapeutic drug doses. All the beneficial effects are due to riluzole action on the TREK‐1 potassium channel, which plays a central role in its therapeutic action. Riluzole has no negative effect on oxaliplatin antiproliferative capacity in human colorectal cancer cells and on its anticancer effect in a mouse model of colorectal cancer. Moreover, riluzole decreases human colorectal cancer cell line viability in vitro and inhibits polyp development in vivo. The present data in mice may support the need to clinically test riluzole in oxaliplatin‐treated cancer patients and state for the important role of the TREK‐1 channel in pain perception. HighlightsRiluzole prevents oxaliplatin‐induced neuropathic adverse effects and comorbidities in mice.The TREK‐1 channel plays a central role in riluzole –induced anti neuropathic effect.Riluzole did not alter oxaliplatin‐induced anticancer effect in vitro and in vivo.Riluzole, per se, decreases human colorectal cancer cell line viability in vitro.Riluzole, per se, inhibits colorectal polyp development in mice.