Protective effects of the mechanistic target of rapamycin against excess iron and ferroptosis in cardiomyocytes

Clinical studies have suggested that myocardial iron is a risk factor for left ventricular remodeling in patients after myocardial infarction. Ferroptosis has recently been reported as a mechanism of iron-dependent nonapoptotic cell death. However, ferroptosis in the heart is not well understood. Mechanistic target of rapamycin (mTOR) protects the heart against pathological stimuli such as ischemia. To define the role of cardiac mTOR on cell survival in iron-mediated cell death, we examined cardiomyocyte (CM) cell viability under excess iron and ferroptosis conditions. Adult mouse CMs were isolated from cardiac-specific mTOR transgenic mice, cardiac-specific mTOR knockout mice, or control mice. CMs were treated with ferric iron [Fe(III)]-citrate, erastin, a class 1 ferroptosis inducer, or Ras-selective lethal 3 (RSL3), a class 2 ferroptosis inducer. Live/dead cell viability assays revealed that Fe(III)-citrate, erastin, and RSL3 induced cell death. Cotreatment with ferrostatin-1, a ferroptosis inhibitor, inhibited cell death in all conditions. mTOR overexpression suppressed Fe(III)-citrate, erastin, and RSL3-induced cell death, whereas mTOR deletion exaggerated cell death in these conditions. 2',7'-Dichlorodihydrofluorescein diacetate measurement of reactive oxygen species (ROS) production showed that erastin-induced ROS production was significantly lower in mTOR transgenic versus control CMs. These findings suggest that ferroptosis is a significant type of cell death in CMs and that mTOR plays an important role in protecting CMs against excess iron and ferroptosis, at least in part, by regulating ROS production. Understanding the effects of mTOR in preventing iron-mediated cell death will provide a new therapy for patients with myocardial infarction. NEW & NOTEWORTHY Ferroptosis has recently been reported as a new form of iron-dependent nonapoptotic cell death. However, ferroptosis in the heart is not well characterized. Using cultured adult mouse cardiomyocytes, we demonstrated that the mechanistic target of rapamycin plays an important role in protecting cardiomyocytes against excess iron and ferroptosis.

Ketamine Analog Methoxetamine Induced Inflammation and Dysfunction of Bladder in Rats

The novel synthetic psychoactive ketamine analog methoxetamine is reportedly being used for recreational purposes. As ketamine use can result in urinary dysfunction, we conducted the present study to investigate how methoxetamine affects the bladder. A cystometry investigation showed that female Sprague-Dawley rats experienced increased micturition frequency bladder dysfunction after receiving a daily intraperitoneal injection of 30 mg/kg methoxetamine or ketamine for periods of 4 or 12 weeks. Histologic examinations of rat bladder tissue revealed damaged urothelium barriers, as well as evidence of inflammatory cell infiltration and matrix deposition. The drug-treated rats showed significantly upregulated levels of pro-inflammatory cytokines such as IL-1β, IL-6, CCL-2, CXCL-1, CXCL-10, NGF, and COX-2. In addition, interstitial fibrosis was confirmed by increased levels of collagen I, collagen III, fibronectin and TGF-β. Besides direct toxic effect on human urothelial cells, methoxetaminealso induced the upregulation related cytokines. Our results indicate that long term methoxetamine treatment can induce bladder dysfunction and inflammation in rats. Methoxetamine was confirmed to produce direct toxic and pro-inflammatory effects on human urothelial cells. Methoxetamine-associated bladder impairment may be similar to ketamine-induced cystitis.

Here today, gone tomorrow…and back again? A review of herbal marijuana alternatives (K2, Spice), synthetic cathinones (bath salts), kratom, Salvia divinorum, methoxetamine, and piperazines

Despite their widespread Internet availability and use, many of the new drugs of abuse remain unfamiliar to health care providers. The herbal marijuana alternatives, like K2 or Spice, are a group of herbal blends that contain a mixture of plant matter in addition to chemical grade synthetic cannabinoids. The synthetic cathinones, commonly called "bath salts," have resulted in nationwide emergency department visits for severe agitation, sympathomimetic toxicity, and death. Kratom, a plant product derived from Mitragyna speciosa Korth, has opioid-like effects, and has been used for the treatment of chronic pain and amelioration of opioid-withdrawal symptoms. Salvia divinorum is a hallucinogen with unique pharmacology that has therapeutic potential but has been banned in many states due to concerns regarding its psychiatric effects. Methoxetamine has recently become available via the Internet and is marked as "legal ketamine." Moreover, the piperazine derivatives, a class of amphetamine-like compounds that includes BZP and TMFPP, are making a resurgence as "legal Ecstasy." These psychoactives are available via the Internet, frequently legal, and often perceived as safe by the public. Unfortunately, these drugs often have adverse effects, which range from minimal to life-threatening. Health care providers must be familiar with these important new classes of drugs. This paper discusses the background, pharmacology, clinical effects, detection, and management of synthetic cannabinoid, synthetic cathinone, methoxetamine, and piperazine exposures.

Review of the toxicology of three alkyl diamines

Three alkyl diamines, which are by-products formed and separated during the production of hexamethylene diamine, have been tested, mostly for their acute toxicity. This paper reviews methodologies used and the results obtained from these three chemicals. All three tested [2-methyl-1,5-pentanediamine (2-MP), 1,3-diaminopentane (DAMP), and 1,2-cyclohexanediamine (DCH)] were 95% pure and were supplied by the DuPont Company. The acute toxicity of all three chemicals is relatively low with acute oral lethal levels in the rat ranging from 1000 to 2300 mg/kg. Single 4-h inhalation exposures show similarly low toxicity with lethality produced in the rat at concentrations ranging from 2.9 to 4.3 mg/L. These diamines are severe skin irritants in both the rabbit and the guinea pig and are also severe eye irritants (studied only in 2-MP). Dermal sensitization was seen in the guinea pig with DAMP and DCH but not with 2-MP. The irritant dose of these materials was shown in repeated exposure inhalation studies when 2-MP and DCH produced irritation in the upper respiratory tract (point of contact) with some lower lung involvement but no significant systemic effects. 2-MP when fed to rats produced a slight body weight effect at dose equivalents of 800 mg/kg with no other parameters affected. All three materials were inactive in Salmonella, and 2-MP did not produce chromosomal aberrations in cultured human lymphocytes. The main effects of this series of diamines appear related to their irritant properties, and attention needs to be paid to their delayed hypersensitivity potential.

Mobilization of iron from cells by hydroxyquinoline-based chelators

With the aim of identifying an iron (Fe) chelator which is effective at mobilizing intracellular Fe, two novel ligands were synthesized and tested. Hydroxyquinoline is known to possess a high affinity for Fe and was thus chosen as the Fe binding motif for the hexadentate chelators, C1 (2,2'-[ethane-1,2-diylbis(iminomethylene)]diquinolin-8-ol) and C2 (2,2'-[cyclohexane-1,2-diylbis(iminomethylene)]diquinolin-8-ol). Both chelators are lipophilic, with Fe3+ complexes slightly more hydrophilic than the free ligands. C1 and C2 were equally toxic to K562 cells, and partial protection was afforded by supplementing the culture medium with human holotransferrin, suggesting that some of the toxicity of the ligands is due to cellular Fe depletion. Micromolar concentrations of both ligands effectively mobilized 59Fe from reticulocytes and K562 cells. In reticulocytes, 50 microM C1 caused the release of 60% of the cells' initial 59Fe uptake after a 4h incubation. Under the same conditions, C2 revealed a release of 50% of the 59Fe. Overall, both ligands merit in vivo study for oral activity. Their effectiveness at low concentrations makes them candidates for therapeutic use.

Novel cytotoxic chelators that bind iron(II) selectively over zinc(II) under aqueous aerobic conditions

To achieve cellular iron deprivation by chelation, it is important to develop chelators with selective metal-binding properties. Selectivity for iron has long been the province of certain oxygen-donor chelators such as desferrioxamine, which target Fe(III) and exploit the strength of a relatively ionic Fe(III)-O interaction. We have been studying novel chelators that possess mechanisms to selectively chelate +2 biometals, particularly tachpyr [N,N',N"-tris(2-pyridylmethyl)-1,3,5-cis,cis-triaminocyclohexane] and derivatives from N,N',N"-trialkylation and pyridine ring alkylation. Metal-exchange and metal-binding competition reactions have been conducted at pH 7.4, 37 degrees C and time periods until no further change was observed (generally 24-48 h). Under anaerobic conditions, tachpyr is strongly selective for iron, binding 95+/-5% Fe(II) versus 5+/-5% Zn(II) in the forms [Fe(tachpyr)](2+) and [Zn(tachpyr)](2+) respectively. Under aerobic conditions, tachpyr complexes Fe(II) more effectively than Fe(III), forming iminopyridyl complexes [Fe(tachpyr-ox-n)](2+) (n=2, 4) by O(2)-induced and iron-mediated oxidative dehydrogenation. Complexes [Fe(tachpyr-ox-n)](2+) are also strongly bound forms of iron that are unaffected by an excess of Zn(II) (75 mol zinc:1 mol iron complex). The preference of tachpyr for iron over zinc under aerobic conditions appears to be hindered by oxidation of Fe(II) to Fe(III), such that the proportions bound are 44+/-10% Fe(II) versus 56+/-10% Zn(II), in the respective forms [Fe(tachpyr-ox-n)](2+) and [Zn(tachpyr)](2+). However, upon addition of the reducing agent Na(2)S(2)O(4) that converts Fe(III) to Fe(II), the binding proportions shift to 76+/-10% Fe(II) versus 24+/-10% Zn(II), demonstrating a clear preference of tachpyr for Fe(II) over Zn(II). Iron(II) is in the low-spin state in [Fe(tachpyr)](2+) and [Fe(tachpyr-ox-n)](2+) (n=2, 4), which is a likely cause of the observed selectivity. N-methylation of tachpyr [giving (N-methyl)(3)tachpyr] results in the loss of selectivity for Fe(II), which is attributed to the steric effect of the methyl groups and a resulting high-spin state of Fe(II) in [Fe(N-methyl)(3)tachpyr)](2+). The relationship of chelator selectivity to cytotoxicity in the tach family will be discussed.

Mechanisms underlying the cytotoxic effects of Tachpyr--a novel metal chelator

Tachpyr (N,N'N"-tris(2-pyridylmethyl)-cis,cis-1,3,5-triaminocyclohexane), a novel metal chelator, was previously shown to deplete intracellular iron and exert a cytotoxic effect on cultured bladder cancer cells. Tachpyr binds Fe(II) and readily reduces Fe(III). The iron(II)-Tachpyr chelate undergoes intramolecular oxidative dehydrogenation resulting in mono- and diimino Fe(II) complexes. The present study investigates the redox-activity of the Tachpyr-iron complex to better define the mechanism of Tachpyr's cytotoxicity. Tachpyr's mechanism of cytotoxicity was studied using cell-free solutions, isolated DNA, and cultured mammalian cells by employing UV-VIS spectrophotometry, oximetry, spin-trapping technique, and electron paramagnetic resonance (EPR) spectrometry. The results show that: (1) Tachpyr by itself after 24 h of incubation had a cytotoxic effect on cultured cells; (2) fully oxidized Tachpyr had no cytotoxic effects on cultured cells even after 24 h of incubation; (3) Tachpyr protected isolated DNA against H(2)O(2)-induced damage, but not against HX/XO-induced damage; and (4) Tachpyr-Fe(II) chelate slows down but does not block oxidation of Fe(II), allows O*(-)(2)-induced or Tachpyr-induced reduction of Fe(III), and consequently promotes production of *OH through the Haber-Weiss reaction cycle. The results indicate that Tachpyr can protect cells against short-term, metal-mediated damage. However, upon prolonged incubation, Tachpyr exerts cytotoxic effects. Therefore, in addition to iron depletion, low-level oxidative stress, which in part occurs because of redox cycling of the coordinated iron ion, may contribute to the cytotoxic effects of Tachpyr.

Physiological and hemolytic toxicity of some aminophosphonates

The effect of novel synthesized aminophosphonates on membrane potential and electrical conductance of internodal cells of Nitellopsis obtusa and hemolysis of erythrocytes (RBC) was studied. It was found that those the organophosphorous compounds, when present at 10-100 microM concentrations, caused depolarization and increased electrical conductance of alga membranes. They also influenced fluidity of erythrocyte membranes. When used at higher concentrations aminophosphonates caused hemolysis of RBC. The changes observed depended on structural features of the aminophosphonates, i.e., substituents at the carbon, phosphorus and nitrogen atoms, and, most probably, may be the result of direct interaction of the aminophosphonates with the lipid phase of the plasma membrane and the induced structural changes. Two modes of interaction are proposed.

Comparative investigations of hydroxyamine carane derivative and its R,S-diastereoisomers with strong local anesthetic activity

Our previously conducted pharmacological screening led as to the discovery of the strong local anesthetic activity of the compound designated as KP-23. Earlier crystallographic studies revealed that the compound KP-23 crystallized in diastereoisomeric form in lowest symmetry. The aim of these comparative investigations was to evaluate anesthetic activity of KP-23 and its R,S-diastereoisomers, which were synthesized at the Institute of Organic Chemistry, Biochemistry and Biotechnology, Wroclaw University of Technology.

Polyamine analogue antidiarrheals: a structure-activity study

The syntheses of a group of spermine polyamine analogues and their evaluation as antidiarrheals are described. Each compound was assessed in a rodent castor oil-induced diarrhea model for its ability to reduce stool output and weight loss in a dose-dependent manner. The spermine pharmacophore is shown to be an excellent platform from which to construct antidiarrheals. The activity of the compounds is very dependent on both the nature of the terminal alkyl groups and the geometry of the methylene spacers separating the nitrogens. The toxicity profile is also quite dependent on these same structural features. On the basis of subcutaneous dose-response data and toxicity profiles, two compounds, N(1),N(12)-diisopropylspermine and N(1),N(12)-diethylspermine, were taken forward into more complete evaluation. These measurements included formal acute and chronic toxicity trials, drug and metabolic tissue distribution studies, and assessment of the impact of these analogues on tissue polyamine pools. Finally, the remarkable activity of N,N'-bis[3-(ethylamino)propyl]-trans-1,4-cyclohexanediamine underscores the need to further explore this framework as a pharmacophore for the construction of other antidiarrheal agents.

[The anti-arrhythmia activity of new dicyclohexylamide derivatives of N-substituted alpha-aminocarboxylic acids]

Experiments on arrhythmia models showed a high antiarrhythmic activity of new derivatives of dicyclohexylamides of N-replaced alpha-aminocarbonic acids. The new compounds surpassed in intensity and duration of the antiarrhythmic effect the standard agents with classes I and III antiarrhythmic activity. In doing so they raise myocardial electrical stability and prevent sudden development of ventricular fibrillation. According to the mechanism of the antiarrhythmic activity, the new compounds may be related to antiarrhythmic agents possessing the properties of classes I and III.

[A new class-III antiarrhythmic preparation among the dicyclohexylamides of aminocarboxylic acids]

The Institute of Pharmacology, Academy of Medical Sciences, jointly with AWD (Germany) has synthesized and tested a novel class III antiarrhythmic coded AWD-160-275, a derivative of dicyclohexylamides of aminocarboxylic acids. The compound was shown to prolong cardiac repolarization, to increase atrial and ventricular refractory periods, to decrease sinus nodal automatism, and to unchange intraventricular conduction. The compound proved to be superior to the reference drugs in the rate and duration of antiarrhythmic and antifibrillatory action. In therapeutical doses it has no antiarrhythmic effect. The specific feature of the agent is that there is no relation of longer effective refractory periods to the frequency of stimulation. This property may be useful in treating tachyarrhythmias.

Profile of anticonvulsant activity and minimal toxicity of methyl 4-[(p-chlorophenyl)amino]-6-methyl-2-oxo-cyclohex-3-en-1-oate and some prototype antiepileptic drugs in mice and rats

The anticonvulsant and toxic properties of methyl 4-[(p-chlorophenyl)amino]-6-methyl-2-oxocyclohex-3-en-1-oate (ADD 196022), were compared with those of phenytoin (PHT), carbamazepine (CBZ), and valproate (VPA). These compounds were evaluated in mice and rats using well-standardized anticonvulsant testing procedures. Results indicate that ADD 196022 is a very potent anticonvulsant in the maximal electroshock seizure (MES) model. The compound was effective in nontoxic doses after intraperitoneal (i.p.) administration in mice and oral administration in rats. In mice, i.p. administration of ADD 196022 resulted in an ED50 value of 26.2 mg/kg as compared with a value of 6.48 mg/kg for PHT in the same assay. ADD 196022 was more potent that PHT in the oral rat model, having an ED50 value of 5.79 mg/kg as compared to 23.2 mg/kg for PHT. ADD 196022 was ineffective in nontoxic doses against all other seizure models evaluated and thus has a pharmacologic profile similar to that of PHT.

Modulation of cytotoxicity and cellular pharmacology of 1,2-diaminocyclohexane platinum (IV) complexes mediated by axial and equatorial ligands

Isomers (R,R-, S,S-, and cis-) of 1,2-diaminocyclohexane (DACH) platinum(IV) complexes with selected axial and equatorial ligands were synthesized and evaluated for in vitro antitumor activity, cellular uptake, and total DNA-Pt adducts. L1210 cells, sensitive to cis-diamminedichloroplatinum(II) (CDDP) and tetraplatin (L1210/0), 160-fold resistant to CDDP [L1210/diamminedichloroplatinum (DDP)], or 70-fold resistant to tetraplatin (L1210/DACH), were used in conjunction with compounds having the general structure DACH-Pt(IV)-X2Y2, where X and Y are axial and equatorial ligands and X2Y2 are specifically Cl2Cl2,Ac2Cl2, (TFA)2Cl2, (OH)2Cl2, and Cl2CBDCA (Cl, chloro; Ac, acetato; TFA, trifluoroacetato; OH, hydroxo; CBDCA, 1,1-cyclobutanedicarboxylato). Comparison of cytotoxicities between isomers of Cl2Cl2,Ac2Cl2, or Cl2CBDCA indicated that R,R-isomers were the most effective against all three cell lines. The relatively lower activity of the S,S- and cis-isomers was cell line dependent: against L1210/DACH, both isomers of Cl2Cl2 were only 2- to 3-fold less effective, and this contrasted with 7- and 26-fold lower cytotoxicities, respectively, against L1210/DDP. Cross-resistance factors in the L1210/DDP and L1210/DACH lines depended on both isomeric form and the nature of axial or equatorial ligand. The L1210/DDP cells were 6- to 9-fold cross-resistant to the R,R-isomer, 8- to 15-fold to S,S-isomer, and 13- to 38-fold to cis-isomer. The L1210/DACH line was only 4- to 7-fold cross-resistant to the three isomers of Ac2Cl2 but cross-resistance to the isomers was 47- to 79-fold for Cl2Cl2 and 22- to 56-fold for Cl2CBDCA complexes. Compared with CDDP, accumulation (2 h at 100 microM drug concentration) of Ac2Cl2 in the three L1210 cell lines was 26-50%, while uptake of Cl2Cl2 and (TFA)2Cl2 was 100-170% and 320-570%, respectively. The greatest DNA binding was seen with Cl2Cl2 in all cell lines, followed by (TFA)2Cl2, CDDP, and Ac2Cl2. DNA binding correlated directly with potency (1/concentration producing 50% inhibition) in the L1210/0 model (r = 0.973, P < 0.016) but not in the L1210/DDP and L1210/DACH models. Accumulation and DNA-binding studies indicated that binding efficiency to DNA was: Cl2Cl2 > Ac2Cl2 > CDDP > (TFA)2Cl2. In a nonreducing environment, the Pt(IV) complexes (20 microM) did not react with salmon sperm DNA. Reduced glutathione (100 microM), as a reducing agent, rendered full binding capacity to Cl2Cl2; binding was 25-30% of the expected maximum for (TFA)2Cl2, while Ac2Cl2 remained inert.(ABSTRACT TRUNCATED AT 400 WORDS)

Anticonvulsant 1-phenylcycloalkylamines: two analogues with low motor toxicity when orally administered

1-Phenylcyclohexylamine (PCA) and its analogues 1-phenylcyclopentylamine (PPA) and 1-(3-fluorophenyl)cyclohexylamine (3-F-PCA) are potent anticonvulsants in the mouse maximal electroshock (MES) seizure test. Unlike the structurally related dissociative anesthetic phencyclidine (PCP), however, which produces motor toxicity at anticonvulsant doses, PCA, PPA, and 3-F-PCA protect against MES seizures at 2.2- to 3.5-fold lower doses than those that cause motor toxicity when administered intraperitoneally (i.p.). In the present study, we evaluated the oral anticonvulsant activity of PCA, PPA, and 3-F-PCA in mice; we also examined 3-F-PCA in rats. All the compounds were orally active in the mouse MES seizure test (ED50 values 14.5, 53.4, and 26.7 mg/kg, respectively). Moreover, 3-F-PCA was especially potent in rats, either when administered i.p. (ED50 0.4 mg/kg vs. 9.4 mg/kg in mice) or orally (ED50 0.8 mg/kg). Surprisingly, however, oral PPA failed to cause motor toxicity in mice even at doses that were many times higher than those that were protective in the MES test (TD50 greater than 300 mg/kg). In rats, 3-F-PCA also showed a strikingly low oral toxicity (TD50 greater than 50 mg/kg) in relation to its potency as an anticonvulsant. Like PCP, PCA analogues block N-methyl-D-aspartate (NMDA)-induced behavioral effects and lethality in mice. Moreover, in vitro studies indicate that the compounds act as uncompetitive antagonists of the NMDA receptor-channel complex. Therefore, their anticonvulsant activity may, at least in part, relate to an interaction with NMDA receptors.

Toxicity of 1,4-bis(aminocyclohexyl)methane

1,4-Bis(aminocyclohexyl)methane (PACM; CAS No. 1761-71-3) is a white solid considered for use in polymeric systems. PACM is moderately toxic systemically, with the acute oral lethal dose in rats between 670 and 1000 mg kg-1. PACM is a weak dermal sensitizer in the guinea pig. Instillation of as little as 10 mg of PACM to the rabbit eye produces severe injury. This damage could be permanent and was not reduced by rinsing the eye with water. Dogs given oral doses of 50 mg PACM kg-1 5 days per week for up to 18 months showed kidney and liver damage, along with local irritation of the gastrointestinal tract. The chemical is highly irritating and contact with it should be avoided.

The morphogenesis of cyclohexylamine-induced testicular atrophy in the rat: in vivo and in vitro studies

Male Wistar strain rats were fed a diet providing an intake of 0 or 400 mg cyclohexylamine (CHA)/kg body weight/day for 1, 3, 7, 9, or 13 weeks. At the end of the appropriate feeding period the rats were perfused-fixed with Karnovsky's fixative. The weights of the fixed testes were recorded and the testes, epididymides, and spermatic cord were sampled and processed into methacrylate resin. Histopathological examination of the testes showed changes after 3 weeks of CHA administration. The most frequent and consistent lesion consisted of a focal, basal vacuolation of the Sertoli cell cytoplasm associated with the local loss of spermatocytes and spermatogonia. After a 7-week administration, the Sertoli cell vacuolation was extensive, while the germ cell population showed mild to moderate degeneration and depletion. After longer periods of treatment the lesion was more severe and affected a greater number of tubules leading to general disruption of the germinal epithelium. Cocultures of Sertoli and germ cells were prepared from the testes of Wistar strain rats and exposed to (CHA) or its metabolite 4-aminocyclohexanol (4ACH) at concentrations ranging from 0.1 to 10 mM for periods of 24-72 hr. The cultures were fixed, stained, and examined by light microscopy. Cultures exposed to CHA or 4ACH showed morphological changes comparable with those seen in vivo. Sertoli cell vacuolation was the earliest change with progressive germ cell degeneration and exfoliation from the Sertoli cell monolayer. At equimolar concentrations, CHA produced more marked changes than 4ACH. These results suggest that CHA itself acts directly on the testis and that its primary cellular target is the Sertoli cell.

Ultrastructural changes in rat Clara cells induced by bis(4-amino-3-methylcyclohexyl)methane

Repeated oral administration of bis(4-amino-3-methylcyclohexyl)methane to rats induced unusual ultrastructural changes in Clara cells of the bronchiolar epithelium, involving marked accumulation of electron-dense inclusion bodies with a lamellar structure in the cytoplasm. The appearance of the inclusion bodies was speculated to result from accumulation of complexes formed between the agent and phospholipids within lysosomes, a condition known as drug-induced lipidosis. This finding appeared noteworthy, since it might reflect high potential for metabolism of xenobiotic compounds in Clara cells.

Anticonvulsant activities of 1-phenylcyclohexylamine and its conformationally restricted analog 1,1-pentamethylenetetrahydroisoquinoline

1-Phenylcyclohexylamine (PCA), an analog of phenyclidine (PCP) in which the piperidine ring is replaced by a primary amino group, and its conformationally restricted analog 1,1-pentamethylenetetrahydroisoquinoline (PM-THIQ) were potent anticonvulsants in the mouse maximal electroshock (MES) seizure test (ED50 values, 7.0 and 14.3 mg/kg, respectively). At higher doses, the drugs caused motor impairment (TD50 values, 16.3 and 43.0 mg/kg) and blocked the behavioral effects and lethality of i.p. injected N-methyl-D-aspartate (NMDA) (ED50 values, 36.3 and 127 mg/kg). The separation in potencies in the MES seizure and motor toxicity tests of PCA and PM-THIQ contrasts with PCP which was equally potent in both tests. Several compounds that were structurally related to PM-THIQ (N-ethyl-PCA, 2-methyl-PCA, N-methyl-PM-THIQ, tetrahydroisoquinoline and benzylamine) also blocked MES seizures and caused motor impairment, but failed to show as great a separation between MES anticonvulsant activity and motor toxicity. None of the compounds protected against seizures induced by the chemoconvulsant pentylenetetrazol at doses that lacked motor toxicity. The drugs were also evaluated for their ability to displace [3H]-1-[1-(2-thienyl)-cyclohexyl]piperidine from binding to high affinity acceptor sites (presumably on NMDA receptor-coupled channels) in rat brain homogenates. The rank order of potencies in the binding assay was similar to that in the behavioral tests, except for 2-methyl-PCA which was behaviorally more potent than expected.(ABSTRACT TRUNCATED AT 250 WORDS)

The pharmacokinetics and tissue concentrations of cyclohexylamine in rats and mice

Cyclohexylamine showed dose-dependent kinetics after administration of single oral doses up to 500 mg/kg in rats, with a reduction in plasma clearance, an increase in apparent half-life, and an increased area under the testicular concentration-time curve. Cyclohexylamine was absorbed and eliminated more rapidly by mice. Saturation of cyclohexylamine uptake by rat renal cortical slices in vitro and of renal tubular secretion in vivo occurred at concentrations and doses comparable to the oral dose studies. During chronic dietary administration the concentrations of cyclohexylamine in the plasma and testes showed a pronounced diurnal variation in rats which was not detected in mice. The steady-state plasma clearance in rats was approximately one-half that in mice. The concentrations of cyclohexylamine in the plasma and testes of rats, but not mice, showed a nonlinear relationship to dietary intake. Elevated concentrations were found at intakes greater than 200 mg/kg/day. The pharmacokinetics of cyclohexylamine make an important contribution to the difference in sensitivity to testicular atrophy in rats and mice and the dose-response relationship for this toxicity in rats.

The metabolism and testicular toxicity of cyclohexylamine in rats and mice during chronic dietary administration

Cyclohexylamine hydrochloride has been given in the diet to mice and to Wistar and DA rats for 13 weeks, to provide a constant intake of 400 mg of the base/kg/day. Significantly decreased food intake and body weight gain were found in both strains of rats but not mice. The metabolism of [14C]cyclohexylamine was widely different in Wistar and DA rats and in rats and mice, and these differences were not altered appreciably by chronic intake for 13 weeks. The differences in metabolism resulted in marked and persistent differences in the concentrations of the hydroxylated metabolites in the plasma and testes of treated animals with Wistar much greater than DA much greater than mice. After 7 and 13 weeks testicular atrophy was demonstrated in both strains of rats given cyclohexylamine diet by a decrease in organ weight and by histological changes. DA rats appeared more sensitive to testicular toxicity from cyclohexylamine than Wistar rats, while mice showed no evidence of testicular damage. These data show that the development of testicular toxicity is not related to the extent of hydroxylation. The concentrations of cyclohexylamine in the plasma and testes of the treated animals were lower in mice than in either strain of rats despite a similar daily intake. This suggests that species differences in pharmacokinetics may contribute to the apparent difference in sensitivity to testicular toxicity.

Metabolism of cyclamate and its conversion to cyclohexylamine

Since cyclamates were first introduced in the early 1950s, arguments have raged over the potential carcinogenicity of this artificial sweetener. Concern over the safety of cyclamates arises from observations that some individuals and experimental animals can metabolize cyclamate to cyclohexylamine and that cyclohexylamine has been shown to produce testicular atrophy in experimental animals. This study examines the absorption, excretion, and metabolism of cyclamate, particularly its conversion to cyclohexylamine. In addition, the potential toxicity and pharmacology of cyclohexylamine are discussed.

Structure-activity relationships of airway irritating aliphatic amines. Receptor activation mechanisms and predicted industrial exposure limits

Sensory irritation due to inhalation of diethyl-, triethyl-, dibutyl-, tributyl- and cyclohexylamine was estimated from the decrease in respiratory rate in normal mice (American Standard Method E981-84). The concentration-effect relations followed Michaelis-Menten equations, except for diethylamine, for which a threshold was found. The concentrations depressing the respiratory rate by 50% (RD50) for diethyl-, triethyl-, dibutyl- and cyclohexylamine were 184, 186, 81 and 27 ppm, respectively. For tributylamine the maximum response was too low to achieve a RD50 value. Pulmonary irritation was estimated from the decrease in respiratory rate in tracheal-cannulated mice. The respective concentrations depressing the respiratory rate by 50% (tRD50) were 549, 691, 101, 96 and 78 ppm for diethyl-, triethyl-, dibutyl-, tributyl- and cyclohexylamine. Only minor or no effects on the tidal volumes were found at the lower exposure concentrations. The trigeminal and pulmonary receptors are believed to be activated directly by the amines, and the receptor environments are believed to be lipophilic. Structure-activity analysis was made by comparing the effects of the amines with the effects of previously investigated primary n-alkylamines. Occupational exposure limits (TLV) were estimated for both effects. Finally, the sensory irritation effect was found to be an important part of the odour sensation, also below the TLVs.

Clinico-pathological changes induced in rats treated with amine-curing agent for epoxy resin, bis(4-amino-3-methylcyclohexyl)methane

Amine-curing agent for epoxy resin, bis(4-amino-3-methyl-cyclohexyl)methane (commercial name; Laromin C) has been suspected to have induced in the workers some toxic signs such as collagen disease like scleroderma or polymyositis. Subacute toxicity of this agent was studied in rats following repeated oral administration. The agent was given orally at 5 dose levels (25 mg/kg to 100 mg/kg per one dose) for periods ranging from 10 days to 4 weeks. After the completion of administration, clinico-biochemical tests and histopathological examinations were carried out. In a few cases, skeletal muscles and choroid plexus of the brain were examined by electronmicroscopy. Clinico-biochemical tests revealed some elevation of muscle-derived components such as GOT and CPK as seen in the myopathic diseases. Histologically, various degrees of atrophy, degeneration and regeneration of muscle fibers and a numerical increase of interstitial cells were observed in the skeletal muscles. Electronmicroscopical examination of the gastrocnemius muscle revealed intrasarcoplasmic osmiophilic round-shaped inclusion bodies, sometimes with lamellar structure, which were suggestive of some lipidosis. The epithelial cells of choroid plexus in the brain ventricles represented various degrees of vacuolar changes lightmicroscopically, which were suggested to be dilated smooth endoplasmic reticulum electronmicroscopically. Although scleroderma-like changes were not observed in our experiments, the results suggest that this amine-curing agent for epoxy resin could be one of the causative agents which induced toxic lesions like some collagen diseases including muscle lesions in the workers. In addition, it is considered that the agent may have systemic toxic effects.

Toxicological aspects of cyclamate and cyclohexylamine

In the late 1960s the artificial sweetener cyclamate was implicated as a bladder carcinogen in rats. This finding and other concerns about its safety ultimately led to a ban on cyclamate in the U.S. and restrictions on its use in many other countries. Since that time, the carcinogenic potential of cyclamate and cyclohexylamine, its principal metabolite, has been reevaluated in a group of well-controlled, well-designed bioassays that have failed to substantiate the earlier findings. This review of the published and unpublished literature on cyclamate attempts to evaluate the carcinogenicity question and other important aspects of the toxicity of cyclamate and cyclohexylamine, including their effects on various organ systems, their genotoxic potential, and their effects on reproduction. In addition, the physiological disposition of cyclamate is reviewed, with particular attention directed toward the site and extent of its conversion to cyclohexylamine.

[Subacute toxicity of an amine-curing agent for epoxy resin]

Amine-curing agent for epoxy resin, bis(4-amino-3-methylcyclohexyl)methane, has been suspected of inducing toxic symptoms in man which resemble collagen disease such as scleroderma or polymyositis. We studied subacute toxicity of this agent by repeated oral administrations to rats. The agent was administered 25, 37.5, 50, 75 or 100 mg/kg per one dose, 8 times in 10 days or 17 times in 4 weeks or 20-22 times in 4 weeks. When administration had been completed, clinical biochemical tests and histopathological examinations were carried out. Animals of high dosage group showed suppression of body weight increase and loss of muscular strength of limbs in the administration period. By clinical biochemical tests, elevation of blood components from muscle (CPK, GOT, creatine) was noticed. Also, increase of monoamine oxidase and decrease of alkaline phosphatase were revealed. By histological examinations, skeletal muscle and choroid plexus of brain showed noticeable changes. In muscles of high dosage group, atrophy, degeneration and regeneration of muscle fibers were observed and an increase of fibroblasts was also seen. In choroid plexus, vacuolar changes in epithelial cells were observed, being clearly dose-dependent. No particular change was recognized in skin. Though scleroderma-like change was not observed in the skin histologically, our results suggest that this amine-curing agent was greatly associated with muscle symptoms in the workers who handled epoxy resin and that it was one of causative agents which induced toxic symptoms like those of collagen disease.

Studies of saccharin and cyclohexylamine in a coupled microsomal activating/embryo culture system

Rat embryos undergoing organogenesis (day 10.5 of pregnancy) were exposed to 1.0 mM-saccharin or 0.1, 0.3 or 1.0 mM-cyclohexylamine in an in vitro metabolic activating/embryo culture system. Either in the absence or presence of a metabolic activating system, 1.0 mM-saccharin had few adverse effects on yolk-sac growth or embryo growth or differentiation. However, rat embryos cultured in vitro with cyclohexylamine and an adult rat hepatic microsomal activating system showed more growth retardation and dysmorphogenicity than embryos exposed to the same concentrations of cyclohexylamine alone. A concentration of 1.0 mM-cyclohexylamine alone reduced yolk-sac DNA content (by 51%), embryo DNA content (69%) and crown-rump length (26%). In the presence of a hepatic microsomal activating system this same dose of cyclohexylamine decreased yolk-sac DNA (60%), embryo DNA (84%) and crown-rump length (49%). The effects of the metabolic activating system and of cyclohexylamine were additive. Other than decreasing final embryo DNA content, exposure to 0.1 and 0.3 mM-cyclohexylamine did not produce any deleterious effects on in vitro rat embryo growth or differentiation. Thus a substantial concentration of saccharin (1.0 mM) or cyclohexylamine (0.3 mM) in vitro did not elicit markedly deleterious effects on rat organogenesis, a result in keeping with published in vivo findings.

The effect of cyclohexylamine on the embryo following oral administration to mice and rats

The possible embryotoxic effects of cyclohexylamine hydrochloride doses (expressed as free base) of 10, 30 and 100 mg/kg of body weight per day administered orally in water to mice and rats from the 6th to 15th day post-coitum were investigated. Treatment with daily doses of up to 100 mg/kg of body weight to mice and of up to 30 mg/kg to rats had no adverse effect on the mothers and the embryos. In the rat the dose of 100 mg/kg led to decreased weight gain in the mothers during the treatment period. In parallel, a non-specific retardation of the embryo was found, since the weight of the foetus and of the placenta were significantly reduced. Cyclohexylamine had neither a teratogenic effect nor a primary toxic effect on the embryo in either of the animal species. The tolerated dose without any harm for the development of the embryo was 100 mg/kg/day in mice and 30 mg/kg/day in rats.

Mutagenicity, tumorigenicity, and electrophilic reactivity of the stereoisomeric platinum(II) complexes of 1,2-diaminocyclohexane

Without external activation, cis- and trans-dichlorodiammineplatinum(II) (DDP) and the cis, trans(-), and trans(+) forms of dichloro-1,2-diaminocyclohexaneplatinum(II) (DDCP) and sulfato-1,2-diaminocyclohexaneplatinum(II) (SHP) showed a 400-fold range of mutagenicity for Salmonella typhimurium TA100 and TA98; they were 2 to 10 times more mutagenic for strain TA100 than for strain TA98. With strain TA100, trans-DDP was less than 0.5% as mutagenic as the cis isomer, which produced 180 revertants/nmol. For the diaminocyclohexane complexes, mutagenic activity was strongly dependent on the stereoisomer of the diaminocyclohexane in the complex. Thus, with strain TA100, the trans(+) forms of DDCP and SHP produced 220 and 66 revertants/nmol, respectively, while the cis and trans(-) isomers induced only 10 and 5% as many revertants as the trans(+) forms. The SHP complexes were the most reactive toward DNA and produced a greater reduction in the transforming activity of Bacillus subtilis DNA after 3-hr reaction times than did the DDP or DDCP complexes. With 20-hr reaction times, all of the platinum complexes showed similar extents of reaction with DNA and caused approximately equal losses of transforming activity. The stereoisomeric form of the diaminocyclohexane ligand of the DDCP or SHP complexes did not affect either the reactivity of the complex with DNA or its ability to reduce the transforming activity of DNA. Significant increases in the number of lung adenomas in A/J mice were induced by multiple i.p. injections of cis-DDP and each of the DDCP and SHP complexes (total doses, 21 to 108 mumol/kg body weight). Similar treatments with cis-DDP caused a significant increase in the number of skin papillomas in female CD-1 mice given promoting treatments with croton oil; the DDCP and SHP complexes had little or no activity in this system. At these levels, trans-DDP was not active for the induction of either lung adenomas or skin tumors. With the systems used for this study, the mutagenicities and tumorigenicities of the platinum(II) complexes did not correlate with their reported antitumor activities. Further studies appear warranted to determine whether there may be effective antitumor platinum(II) complexes that are not strongly mutagenic or carcinogenic.

Antimitotic and cytotoxic activity of cis-dichlorobis-(cyclohexylamine)platinum(II) on Chinese hamster ovary cells

The antimitotic and cytotoxic effects of cis-dichlorobis(cyclohexylamine)-platinum(II) (cis-HAD) which among Pt complexes used as antitumoral drugs shows the highest therapeutic index (TI) have been compared to those os cis-dichlorodiamine platinum(II) (cis-DDP), the most commonly used drug of this group, using Chinese hamster ovary cell cultures (CHO line). DNA synthesis inhibition, mitotic index, cell viability, chromosome aberrations and cell survival have been taken into account. The data indicates that the antimitotic agent cis-HAD is active only at doses causing high cell mortality and chromosome damage.

Carcinogenicity of deuterium-labeled N-nitroso-N-methylcyclohexylamine in rats

F344 rats were treated with both unlabeled N-nitroso-N-methylcyclohexylamine (NMC) and deuterium-labeled NMC (NMC-d3) in the methyl group. Both compounds were administered in the drinking water at concentrations of 50 and 12.5 mg/liter. The NMC-d3 was not less carcinogenic than the unlabeled NMC, which suggested that oxidation of the methyl group is not a rate-limiting step in the induction of esophageal tumors.

Occupational scleroderma-like disorder occurring in men engaged in the polymerization of epoxy resins

A new occupational disorder characterized by skin sclerosis is described. This disease developed acutely in workmen exposed to the vapor of epoxy resins. Based on animal experiments, an amine [bis(4-amino-3-methyl-cyclohexyl) methane] is suspected of being the causative agent of the skin sclerosis.

Platinate toxicity: past, present, and prospects

Using traditional toxicologic methods, four species were studied for their qualitative and quantitative predictiveness of the toxic effects of cis-dichlorodiammineplatinum(II) in man. Of the four species studied, mouse, monkey, rat, and dog, the latter two gave the best overall results. Using an in vivo rat model, it was found that except for chloroplatinic acid, eight of the tested analogs were less nephrotoxic than the parent drug, cis-dichlorodiammineplatinum(II). The in vitro renal toxicity screen using flounder tubules showed that of the 26 compounds studied, about half were less toxic than the parent compound. This in vitro mini-tox system can be performed about 30 times faster and at one fiftieth the cost of the in vivo model. The in vitro studies also provided evidence that the biochemical site of toxicity of platihates is on ATPases. The latter studies suggested a basis for unifying the mechanistic interpretation of the toxic actions on such disparate target organs as the kidney, nerve, stomach, and inner ear.

Toxicity of chelated mercury

The oral and iv acute toxicities of several mercury chelates were determined in mice in a search for relationships bearing on the effectiveness of various chelating agents in therapy. It was found that the toxicity was independent of the stability constant for the mercury chelate when the toxicity was expressed on a molar basis. For the mercury chelates of sulfhydryl containing chelating agents, the oral toxicity was unexpectedly low, presumably due to the poor absortion of these materials from the G.I. tract. The results suggest that the toxicities of mercury complexes are independent of the stability constant of the complex over the range of stability constant from 10(23) on down, provided chelation does not drastically alter the distribution of the complex in the body.

[Ultrastructure of rat adenohypophysis following exposure to several amines of the polymathylene series]

Adenohypophysis ultrastructure was studied under the effect of dicyclohexylamine nitrite and oil-soluble salt of cyclohexylamine used as inhibitors of the atmospheric corrosion of metals. It is stated that even due to the early effect they cause a morphofunctional rearrangement of the organ in spite of the same reaction of the adenohypophysis cells to M-1 and dicyclohexylamine nitrite the effect of the latter causes more distinct and pronounced changes.

[Electron microscopic study of rat hepatocytes following exposure to dicyclohexylamine nitrite and an oil-soluble salt of cyclohexylamine]

Ultrastructural changes were studied in the rat liver under the effect of dicyclohexylamine nitrite and oil-soluble salt of cyclohexylamine in doses of 1/10 LD50. Both substances are stated to cause damages in the structure of hepatocytes even after three days of exposure. Dicyclohexylamine nitrite shows a more pronounced effect displayed in developed dystrophic changes of cytoplasmic organelles and in the presence of osmiophil bodies.

Long-term and multigeneration toxicity studies with cyclohexylamine hydrochloride

Cyclohexylamine (CHA), the metabolite of cyclamate produced in varying degree by gastrointestinal microorganisms, was subjected to a 2-year multi-generation feeding study in rats, at dosages of 15, 50, 100, and 150 mg/kg/d. Observations included growth, feed efficiency, clinical and hematological tests, reproduction, teratology, mortality and gross and microscopic pathology. Rats from the first litters of each generation from F0 through F4 were mated to produce the next succeeding generation. Those from the second litters of F1 through F4 were also mated, half the dams being delivered by hysterotomy for teratological examination, while litters from the other half were raised to maturity. Except for some non-progressive growth retardation in the higher dosage groups, due to lower food consumption, the physical and clinical observations in the test groups fell substantially within normal limits and were not significantly different from the untreated controls. Reproduction rates were normal in all groups but at the higher dosages the size of the litters and their weaning weights were slightly reduced. At the 150 mg/kg level, histopathological examination revealed mucosal thickening of the bladder walls and evidence of renal calcification; however, no bladder tumors were seen, such as occurred in the chronic feeding study in which rats received 2500 mg/kg of a cyclamate: saccharin (10 : 1) mixture. A significantly higher incidence of testicular atrophy, characteristic of aged rats, was observed in the F0 group at the highest dosage level; however, these males continued to be fertile, in two cases up to 6 consecutive matings.