Leptin in the Commissural Nucleus Tractus Solitarii Increases the Glucose Responses to Carotid Chemoreceptors Activation by Cyanide.

Leptin is a protein hormone that plays a key role in the regulation of energy balance and glucose homeostasis. Leptin and all leptin receptor isoforms are present in the carotid bodies, but its precise function in glucose regulation and metabolism is not yet known. The aim of this study was to determine whether exogenous leptin, microinjected into the commissural nucleus tractus solitarii (cNTS), preceding sodium cyanide (NaCN) injection into the circulatory isolated carotid sinus (ICS), in vivo, modifies hyperglycemic reflex (HR) and brain glucose retention (BGR). In anesthetized Wistar rats (sodium pentobarbital, i.p. 3.3 mg/100 g/saline, Pfizer, Mex), arterial and venous blood samples were collected from silastic catheters implanted in the abdominal aorta and jugular sinus. Exogenous leptin (50 ng/20 nL of aCSF) or leptin vehicle (20 nL of aCSF) microinjected (stereotaxically) into the cNTS 4 min before NaCN (5 µg/100 g/50 µL saline into ICS) (experimental 1 [E1] and control 1[C1] groups, respectively) significantly increased HR and BGR compared with their basal values, but the increase was bigger in the E1 group. When leptin or aCSF were injected into the cNTS before saline (E2 and C2 groups, respectively) glucose responses did not vary when compared with their basal levels. Leptin and its receptors in the cNTS cells probably contribute to their sensitization during hypoxia.

Determinants of cognitive performance in children relying on cyanogenic cassava as staple food.

While risk factors for konzo are known, determinants of cognitive impairment in konzo-affected children remain unknown. We anchored cognitive performance (KABC-II scores) to serum levels of free-thyroxine (free-T4), thyroid-stimulating hormone (TSH), albumin, and motor proficiency (BOT-2 scores) in 40 children including 21 with konzo (median age: 9 years) and 19 without konzo (median age: 8 years). A multiple regression model was used to determine variables associated with changes in KABC-II scores. Age (ß: -0.818, 95% CI: -1.48, -0.152) (p = 0.018), gender (ß: -5.72; 95% CI: -9.87, -1.57 for females) (p = 0.009), BOT-2 score (ß: 0.390; 95% CI: 0.113, 0.667) (p = 0.008), and free-T4 (ß: 1.88; 95% CI: 0.009, 3.74) (p = 0.049) explained 61.1 % of variation in KABC-II scores. Subclinical hypothyroidism was not associated with poor cognition. A crude association was found between serum albumin and KABC-II scores (ß: 1.26; 95 % CI: 0.136, 2.39) (p = 0.029). On spot urinary thiocyanate reached 688 µmol/l in children without konzo and 1,032 µmol/L in those with konzo. Female gender and low serum albumin are risk factors common to cognitive and proportionally associated motor deficits in children exposed to cassava cyanogens. The two types of deficits may share common mechanisms.

Normative concentrations of urine thiocyanate in cassava eating communities in Nigeria.

Exposure to cyanide is a major public health problem where highly cyanogenic cassava foods are consumed. Thiocyanate (SCN), the biomarker of exposure to cyanide is present in several foods, and produced endogenously. Concentrations of urine SCN were measured in endemic and non-endemic areas of ataxic polyneuropathy in Nigeria. Cassava food consumption in the endemic area was twice that of non-endemic areas. Geometrical mean (95% CI) urine SCN was 20 µmol/l (18-24) for no consumption of cassava foods, 56 µmol/l (49-64) for daily consumption, 56 µmol/l (48-65) for twice daily consumption and 85 µmol/l (62-117) for thrice daily consumption. 95th percentile reference limit was 125 µmol/l for no consumption of cassava food, but 360 µmol/l for thrice daily consumption. Urine SCN is a useful biomarker of exposure to cyanide from cassava foods. There is strong ecological association of exposure to cyanide and endemicity of ataxic polyneuropathy.

[Cyanide, in And Then There Were None, Sparkling Cyanide].

And Then There Were None and Sparkling Cyanide, two of Agatha Christie's famous novels describe potassium cyanide-induced deaths. Cyanide, a tasteless, odorless, strongly alkaline poison is a powerful gastrointestinal irritant, following oral ingestion. It reacts with hydrochloric acid in the gastric juice to produce hydrogen cyanide gas, which is absorbed and inhibits the mitochondrial electron transfer system and consequently suppresses adenosine triphosphate (ATP) production. Therefore, the central nervous system, which consumes a large amount of ATP, is first affected and symptoms of poisoning manifest as dizziness, disorientation, coma, and convulsions. The orally lethal dose is approximately 300 mg.

[Alternative means of drug therapy in cancer: letril].

Letril (amygdaline) is one of drugs of alternative therapy for cancer that is used over three decades and relates to cyanogenic glycosides received from kernels of various fruits (almonds, apricots, peaches, etc. The basis of suggestion of letril as antitumor agent is hypotheses about selective fermentative splitting of amygdaline in tumor cells with developing of cyanide that should cause to apoptosis as a result of aerobic glycolysis suppression. None of these assumptions found their experimental confirmation. In clinical trials there was established inefficiency of letril with a very high probability to develop severe cyanide intoxication. Despite obtained scientific data and absence of permission from the supervising institutions (FDA) letril is still advertised, produced and distributed as anti-tumor drug.

Local Targeting of NAD+ Salvage Pathway Alters the Immune Tumor Microenvironment and Enhances Checkpoint Immunotherapy in Glioblastoma.

The aggressive primary brain tumor glioblastoma (GBM) is characterized by aberrant metabolism that fuels its malignant phenotype. Diverse genetic subtypes of malignant glioma are sensitive to selective inhibition of the NAD+ salvage pathway enzyme nicotinamide phosphoribosyltransferase (NAMPT). However, the potential impact of NAD+ depletion on the brain tumor microenvironment has not been elaborated. In addition, systemic toxicity of NAMPT inhibition remains a significant concern. Here we show that microparticle-mediated intratumoral delivery of NAMPT inhibitor GMX1778 induces specific immunologic changes in the tumor microenvironment of murine GBM, characterized by upregulation of immune checkpoint PD-L1, recruitment of CD3+, CD4+, and CD8+ T cells, and reduction of M2-polarized immunosuppressive macrophages. NAD+ depletion and autophagy induced by NAMPT inhibitors mediated the upregulation of PD-L1 transcripts and cell surface protein levels in GBM cells. NAMPT inhibitor modulation of the tumor immune microenvironment was therefore combined with PD-1 checkpoint blockade in vivo, significantly increasing the survival of GBM-bearing animals. Thus, the therapeutic impacts of NAMPT inhibition extended beyond neoplastic cells, shaping surrounding immune effectors. Microparticle delivery and release of NAMPT inhibitor at the tumor site offers a safe and robust means to alter an immune tumor microenvironment that could potentiate checkpoint immunotherapy for glioblastoma. SIGNIFICANCE: Microparticle-mediated local inhibition of NAMPT modulates the tumor immune microenvironment and acts cooperatively with anti-PD-1 checkpoint blockade, offering a combination immunotherapy strategy for the treatment of GBM.

Can excreted thiocyanate be used to detect cyanide exposure in live reef fish?

Cyanide fishing, where a solution of sodium or potassium cyanide is used to stun reef fish for easy capture for the marine aquarium and live fish food trades, continues to be pervasive despite being illegal in many countries and destructive to coral reef ecosystems. Currently, there is no easy, reliable and universally accepted method to detect if a fish has been exposed to cyanide during the capture process. A promising non-invasive technique for detecting thiocyanate ions, the metabolic byproduct excreted by exposed fish, has been reported in the literature. In an effort to validate this method, four cyanide exposure studies on Amphiprion ocellaris (common clownfish) were carried out over three years. Fish were either exposed to the same (25 ppm) or twice the concentration (50 ppm) as the previsouly published method. Over 100 water samples of fish exposed to cyanide were analyzed by reverse phase HPLC with a C30 column treated with polyethylene glycol and UV detector operating at 220 nm. No thiocyanate was detected beyond the analytical standards and positive controls prepared in seawater. As an alternate means of detecting thiocyanate, water samples and thiocyanate standards from these exposures were derivatized with monobromobimane (MBB) for LC-MS/MS analysis. Thiocyanate was detected in standards with concentrations as low as 0.6 µg/L and quantified to 1 µg/L, but thiocyanate could not be detected in any of the water samples from fish exposed to cyanide with this method either, confirming the HPLC results. Further, we calculated both the mass balance of thiocyanate and the resultant plausible dosage of cyanide from the data reported in the previously published method. These calculations, along with the known lethal dosage of cyanide, further suggests that the detection of thiocyanate in aquarium water is not a viable method for assessing fish exposure to cyanide.

Methylene blue counteracts cyanide cardiotoxicity: cellular mechanisms.

In adult left ventricular mouse myocytes, exposure to sodium cyanide (NaCN) in the presence of glucose dose-dependently reduced contraction amplitude, with ~80% of maximal inhibitory effect attained at 100 µM. NaCN (100 µM) exposure for 10 min significantly decreased contraction and intracellular Ca2+ concentration ([Ca2+]i) transient amplitudes, systolic but not diastolic [Ca2+]i, and maximal L-type Ca2+ current ( ICa) amplitude, indicating acute alteration of [Ca2+]i homeostasis largely accounted for the observed excitation-contraction abnormalities. In addition, NaCN depolarized resting membrane potential ( Em), reduced action potential (AP) amplitude, prolonged AP duration at 50% (APD50) and 90% repolarization (APD90), and suppressed depolarization-activated K+ currents but had no effect on Na+-Ca2+ exchange current ( INaCa). NaCN did not affect cellular adenosine triphosphate levels but depolarized mitochondrial membrane potential (ΔΨm) and increased superoxide (O2·-) levels. Methylene blue (MB; 20 µg/ml) added 3 min after NaCN restored contraction and [Ca2+]i transient amplitudes, systolic [Ca2+]i, Em, AP amplitude, APD50, APD90, ICa, depolarization-activated K+ currents, ΔΨm, and O2·- levels toward normal. We conclude that MB reversed NaCN-induced cardiotoxicity by preserving intracellular Ca2+ homeostasis and excitation-contraction coupling ( ICa), minimizing risks of arrhythmias ( Em, AP configuration, and depolarization-activated K+ currents), and reducing O2·- levels. NEW & NOTEWORTHY Cyanide poisoning due to industrial exposure, smoke inhalation, and bioterrorism manifests as cardiogenic shock and requires rapidly effective antidote. In the early stage of cyanide exposure, adenosine triphosphate levels are normal but myocyte contractility is reduced, largely due to alterations in Ca2+ homeostasis because of changes in oxidation-reduction environment of ion channels. Methylene blue, a drug approved by the U.S. Food and Drug Administration, ameliorates cyanide toxicity by normalizing oxidation-reduction state and Ca2+ channel function.

Cardiopulmonary bypass, hemolysis, and nitroprusside-induced cyanide production.

BACKGROUND: Cyanide toxicity is a complication of sodium nitroprusside administration. Cardiac surgery may increase the risk of cyanide toxicity, because hemolysis during cardiopulmonary bypass (CPB) may catalyze the release of free cyanide from sodium nitroprusside. METHODS: We obtained serial blood specimens from 25 cardiac surgical patients during CPB. Plasma specimens were analyzed for free hemoglobin concentration and ability to generate free cyanide anion upon exposure to sodium nitroprusside. RESULTS: Hemolysis based on plasma-free hemoglobin concentration increased over time during CPB at an average rate of 0.27 mg x dL(-1) x min(-1) (P < 0.001). The concentration of free cyanide generated by the addition of sodium nitroprusside to the plasma samples was directly related to the plasma-free hemoglobin concentration (P < 0.001). CONCLUSION: CPB-associated hemolysis and free hemoglobin release accelerated the immediate release of free cyanide from sodium nitroprusside. These in vitro findings suggest that cardiac surgical patients may be at increased risk of cyanide toxicity in response to the perioperative administration of sodium nitroprusside.

Spectrofluorimetric determination of tranexamic acid in hydrogel patch formulations by derivatization with naphthalene-2,3-dicarboxaldehyde/cyanide.

The aim of this research was to develop and validate a spectrofluorimetric method for determination of tranexamic acid in hydrogel patch formulations. Tranexamic acid (trans-4-aminomethylcyclohexanecarboxylic acid, trans-AMCHA) is an antifibrinolytic drug that recently gained attention as a skin-whitening agent due to its inhibitory effect on ultraviolet (UV)-induced pigmentation in vivo. Derivatization with naphthalene-2,3-dicarboxaldehyde (NDA) in the presence of cyanide ion (CN(-)) to produce a fluorescent 1-cyanobenz[f]isoindole (CBI) product (lambda(ex) = 420 nm, lambda(em) = 480 nm) is for the first time reported for the determination of tranexamic acid in hydrogel patch formulations. Other separation techniques were not used in the analysis of the CBI-fluorescent product as required in the previous studies. The developed method was proven to be precise and accurate with percent recoveries ranging between 98.0% and 101.8% at the concentration range of 8.4-84.0 microg/ml (R(2) > 0.999). The intra- and inter-day precisions as expressed by the relative standard deviations (RSD) were below 1.85%. Derivatization of tranexamic acid with NDA/CN(-) was completed within five minutes and was stable for at least 30 minutes. The method has been applied to the analysis of drug content and release profiles in tranexamic hydrogel patch formulations.

Amygdalin, quackery or cure?

BACKGROUND: The cyanogenic diglucoside, amygdalin, has gained high popularity among cancer patients together with, or in place of, conventional therapy. Still, evidence based research on amygdalin is sparse and its benefit controversial. PURPOSE: Since so many cancer patients consume amygdalin, and many clinicians administer it without clear knowledge of its mode of action, current knowledge has been summarized and the pros and cons of its use weighed. METHODS: A retrospective analysis was conducted for amygdalin relevant reports using the PubMed database with the main search term "Amygdalin" or "laetrile", at times combined with "cancer", "patient", "cyanide" or "toxic". We did not exclude any "unwanted" articles. Additionally, internet sources authorized by governmental or national institutions have also been included. SECTIONS: Individual chapters summarize pharmacokinetics, preclinical and clinical studies and toxicity. CONCLUSION: No convincing evidence showing that amygdalin induces rapid, distinct tumor regression in cancer patients, particularly in those with late-stage disease, is apparent. However, there is also no evidence that purified amygdalin, administered in "therapeutic" dosage, causes toxicity. Multiple aspects of amygdalin administration have not yet been adequately explored, making further investigation necessary to evaluate its actual therapeutic potential.

Phase I study and pharmacokinetic of CHS-828, a guanidino-containing compound, administered orally as a single dose every 3 weeks in solid tumours: an ECSG/EORTC study.

CHS 828 is a new guanidino-containing drug. The aim of this study was to determine the maximum tolerated dose (MTD), the recommended dose and the toxicity of CHS 828. CHS 828 was given orally once every 3 weeks. The starting dose was 50 mg, which was escalated to 500 mg. A total of 107 courses was administered to 37 patients. At the 500-mg dose level, two of three patients experienced dose-limiting toxicities (DLT) (grade 3 mucositis and grade 4 thrombocytopenia), establishing this as the MTD. One of seven patients treated at 420 mg dose experienced DLT (grade 4 leucopenia, grade 4 mucositis and grade 4 diarrhoea), and this was considered the recommended dose for phase II studies. Vomiting, haematuria, leucopenia and thrombocytopenia were other significant toxicities. The pharmacokinetics of CHS 828 showed large variations both between and within patients. No objective responses were seen. A dose of 420 mg of CHS 828 administered every 3 weeks is the recommended dose, while 500 mg is the MTD.

A Phase I study of CHS 828 in patients with solid tumor malignancy.

CHS 828 is a cyanoguanidine, which has demonstrated potent antitumor activity in preclinical tumor models. The activity of CHS 828 in vitro showed only low to moderate correlation to other antineoplastic agents suggesting a unique mechanism of action. Ten females and 6 males (median age 58 years) with solid tumors refractory to standard therapy were included in this Phase I study. The study drug was administered to fasting patients as a single oral dose on days 1-5 of each treatment cycle. Patients received one to six cycles of treatment. The doses ranged from 30 mg to 200 mg (total dose within a cycle). Hematological toxicity was generally mild and dominated by transient thrombocytopenia and lymphocytopenia. Nonhematological toxicity most frequently consisted of nausea, vomiting, diarrhea, fatigue, and localized genital mucositis. The dose-limiting toxicities were thrombocytopenia, thrombosis, esophagitis, diarrhea, and constipation. The recommended Phase II dose of CHS 828 was 20 mg once daily for 5 days in cycles of 28 days duration. The extent of systemic exposure of CHS 828 across patients was approximately dose proportional. The time at which the highest drug concentration occurs was 2.2 +/- 1.3 h and half-life was 2.1 +/- 0.52 h (mean +/- SD). Large intra- and interindividual variation in dose level-adjusted maximum plasma concentration and the area under the curve from time 0 h to infinity were observed. There was an apparent inverse relationship between systemic exposure of CHS 828, and thrombocyte and lymphocyte nadir levels. No objective tumor responses were observed, and 7 patients showed stable disease after two courses of therapy.

Dietary cyanide and tropical malnutrition diabetes.

Two categories of diabetes are recognized in the temperate zone--ketosis-prone diabetes requiring insulin and diabetes not requiring insulin. Another unique type of diabetes occurs in the tropics. It has two forms, both different from either form of temperate zone diabetes. Type J and pancreatic diabetes are both characterized by youth onset, antecedent malnutrition, substantial insulin requirement, and resistance to ketosis. In the tropical countries where they are found, both forms are associated with specific dietary practices, including a nutritionally marginal protein intake. The close association with low protein intake distinguishes this form of diabetes from that occurring in North America, Europe, and Oceania. The geographic distribution of malnutrition diabetes, in addition to being limited to the tropics, coincides regularly with the consumption of tapioca (cassava) or other foods that contain cyanide-yielding substances. Ingested cyanide is normally detoxified, principally, by conversion to thiocyanate. This detoxification requires sulfur, derived principally from amino acid sources. Studies in the rat indicate a remarkable ability to detoxify ingested cyanide, a reduction in urinary thiocyanate excretion when protein intake is lowered (especially during growth), production of marked hyperglycemia by either oral or parenteral cyanide, and the development of cyanosis and epidermal changes when there is prolonged exposure to cyanide. Both the association of malnutrition diabetes with food cyanogens and our laboratory observations support a role for cyanide in its pathogenesis.

Cerebral energy metabolism in cyanide encephalopathy.

This study documents the effects of an intracarotid artery injection of a lethal threshold amount of KCN (2.5 mg.kg-1) on the energy metabolism and histology of the rat brain. This dose of KCN resulted in a rapid abolition of electroencephalographic activity, which remained essentially absent for up to 3 h. Cerebral metabolite measurements 0.25 h after KCN infusion indicated a 52% reduction in cytochrome oxidase activity, a 600% increase in lactate, a 32% reduction in ATP, a 73% increase in ADP, and an 85% decrease in glycogen. Measurements of the above energy metabolites over the ensuing 7 days showed a return to control of all metabolites by 6-24 h. Corresponding to the normalization of energy metabolism was a return of EEG and conscious activity. Histological examination of cyanide-exposed animals revealed a paucity of change with only one animal at 0.5 h showing several dark neurons, two animals at 1 h with minor pallor of corpus callosum and caudate-putamen, and one animal at 48 h with a small hippocampal infarction. It is concluded that it may be impossible to produce a serious enough disruption of cerebral metabolism with KCN injection, to produce neuronal damage by purely "histotoxic" mechanisms.

Cardiovascular changes during the calcium carbimide-ethanol interaction.

Potentially serious cardiovascular changes occur in alcoholics as a results of carbimide-ethanol reactions (CERs). Hypotension and tachycardia often occur when blood acetaldehyde levels increase. Hypotension with bradycardia can also occur secondary to vagal stimulation, the results of retching or vomiting. Conservative procedures (e.g., modified Trendelenburg's position) are usually effective in reversing the hypotension but in severe reactions active treatment (intravenous fluids, O2, and drugs) may be indicated. Three case reports are presented to illustrate cardiovascular responses during CERs; for comparison, changes for one subject during a disulfiram reaction are also presented. Caution is recommended in screening alcoholics before treatment with carbimide or disulfiram so as to rule out cardiovascular, hepatic, or renal diseases.

Konzo in the Central African Republic.

We identified a new focus of konzo, an upper motor neuron disease, in a part of western Central African Republic. Interviews and high serum levels of thiocyanate indicate that cyanide exposure from insufficiently processed cassava may cause konzo. Abrupt onset, nonprogressive course, and seronegativity to HTLV-I clearly differentiate konzo from HTLV-I-associated myelopathy in tropical countries.

Guanidino-containing drugs in cancer chemotherapy: biochemical and clinical pharmacology.

The pharmacology and clinical application of three guanidino-containing compounds are reviewed in this commentary with special focus on a new member of this group of drugs, CHS 828 [N-(6-(4-chlorophenoxy)hexyl)-N'-cyano-N"-4-pyridylguanidine]. m-Iodobenzylguanidine (MIBG) and methylglyoxal bis(guanylhydrazone) (MGBG) have been extensively studied, preclinically as well as clinically, and have established use as anticancer agents. MIBG has structural similarities to the neurotransmitter, norepinephrine, and MGBG is a structural analog of the natural polyamine spermidine. CHS 828 is a pyridyl cyanoguanidine newly recognized as having cytotoxic effects when screening antihypertensive compounds. Apart from having the guanidino groups in common, there are many differences between these drugs in both structure and their mechanisms of action. However, they all inhibit mitochondrial function, a seemingly unique feature among chemotherapeutic drugs. In vitro in various cell lines and primary cultures of patient tumor cells and in vivo in various tumor models, CHS 828 has cytotoxic properties unlike any of the standard cytotoxic drugs with which it has been compared. Among these are non-cross-resistance to standard drugs and pronounced activity in tumor models acknowledged to be highly drug-resistant. Similar to MIBG, CHS 828 induces an early increase in extracellular acidification, due to stimulation of the glycolytic flux. Furthermore, ATP levels decrease, and the syntheses of DNA and protein are shut off after approximately 30 hr of exposure, indicating active cell death. CHS 828 is now in early clinical trials, the results of which are eagerly awaited.

Contact dermatitis from cyanide plating solutions.

Two cases of contact dermatitis from electroplating solutions were attributed to irritation from cyanide salts. Both demonstrated similar clinical features. In neither could concomitant contact allergy to other constituents of the plating solutions be demonstrated. In one case, irritation could not be attributed to the alkalinity of the plating solution. Contact dermatitis from cyanide plating solutions may be associated with systemic symptoms, since cyanide is rapidly absorbed through the skin. Poor handling and hygiene techniques in the workplace should be corrected immediately.

Evaluation of cyanide exposure and its effect on thyroid function of workers in a cable industry.

A thyroid-hormone evaluation of workers dealing with cyanide compounds in an electroplating process of a cable industry was carried out. Serum thiocyanate (SCN) levels of 35 nonsmoking copper-ply employees were assayed by a ferric-chloride color test. The mean SCN concentration of these employees was 316 +/- 15 mumol/L, which was significantly (P < 0.01) higher than that of control subjects (90.8 +/- 9.02 mumol/L). Serum thyroxine (T4), triiodothyronine (T3), and thyroid-stimulating hormone (TSH) concentrations of exposed workers were compared with those of 35 control subjects. Cyanide exposure resulted in a decrease in T4 and T3 concentrations (P < 0.05) and an increase in TSH concentration (P < 0.05), compared with the control subjects. The serum T4 level was found to be negatively correlated (r = -0.363, P < 0.05), whereas the TSH level was positively correlated (r = 0.354, P < 0.05), with SCN concentration in the exposed group. The study suggests that occupational cyanide exposure in the industry impairs thyroid function.