Isothiocyanates in medicine: A comprehensive review on phenylethyl-, allyl-, and benzyl-isothiocyanates

In recent years, isothiocyanates (ITCs), bioactive compounds primarily derived from Brassicaceae vegetables and herbs, have gained significant attention within the biomedical field due to their versatile biological effects. This comprehensive review provides an in-depth exploration of the therapeutic potential and individual biological mechanisms of the three specific ITCs phenylethyl isothiocyanate (PEITC), allyl isothiocyanate (AITC), and benzyl isothiocyanate (BITC), as well as their collective impact within the formulation of ANGOCIN® Anti-Infekt N (Angocin). Angocin comprises horseradish root (Armoracia rusticanae radix, 80 mg) and nasturtium (Tropaeoli majoris herba, 200 mg) and is authorized for treating inflammatory diseases affecting the respiratory and urinary tract. The antimicrobial efficacy of this substance has been confirmed both in vitro and in various clinical trials, with its primary effectiveness attributed to ITCs. PEITC, AITC, and BITC exhibit a wide array of health benefits, including potent anti-inflammatory, antioxidant, and antimicrobial properties, along with noteworthy anticancer potentials. Moreover, we highlight their ability to modulate critical biochemical pathways, such as the nuclear factor erythroid 2-related factor 2 (Nrf2)/Kelch-like ECH-associated protein 1 (Keap1), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), and signal transducer and activator of transcription (STAT) pathways, shedding light on their involvement in cellular apoptosis and their intricate role to guide immune responses.

1,8-cineole (eucalyptol): A versatile phytochemical with therapeutic applications across multiple diseases

1,8-cineole (Eucalyptol), a naturally occurring compound derived from botanical sources such as eucalyptus, rosemary, and camphor laurel, has a long history of use in traditional medicine and exhibits an array of biological properties, including anti-inflammatory, antioxidant, antimicrobial, bronchodilatory, analgesic, and pro-apoptotic effects. Recent evidence has also indicated its potential role in managing conditions such as Alzheimer's disease, neuropathic pain, and cancer. This review spotlights the health advantages of 1,8-cineole, as demonstrated in clinical trials involving patients with respiratory disorders, including chronic obstructive pulmonary disease, asthma, bronchitis, and rhinosinusitis. In addition, we shed light on potential therapeutic applications of 1,8-cineole in various conditions, such as depression, epilepsy, peptic ulcer disease, diarrhea, cardiac-related heart diseases, and diabetes mellitus. A comprehensive understanding of 1,8-cineole's pharmacodynamics and safety aspects as well as developing effective formulations, might help to leverage its therapeutic value. This thorough review sets the stage for future research on diverse health benefits and potential uses of 1,8-cineole in tackling complex medical conditions.

590 Influence of Hospital Characteristics on Patient Outcomes Following Cancer Surgery: An International, Mixed Methods Study Across 66 Countries

Aim

Early death after cancer surgery is higher in low- and middle-income settings, yet the impact of hospital characteristics on early postoperative outcomes following cancer surgery worldwide are unknown.

Method

A mixed-methods analysis was performed using data from the GlobalSurg 3 study, a multicentre, international prospective cohort study of patients who underwent surgery for breast, gastric or colorectal cancer. The primary outcomes were 30-day mortality and major complication rates. Hierarchical clustering identified distinct hospital characteristics to create a facility capacity framework. Adjusted outcomes were determined after accounting for patient characteristics and country-income group.

Results

Hospital-level data were available for 9685 patients across 238 hospitals. The facility capacity framework consisted of seven distinct hospital resources and processes: presence of CT scan, postoperative recovery area, critical care facilities, opioid analgesia availability, oncologist, pathology and radiotherapy services. While complication rates were similar across hospitals with varying facility capacities, hospitals with five or less capacities (116 hospitals, 2251 patients) had increased mortality (aOR 1.67, 95% CI 1.13-2.48; P = 0.010). After adjustment for case-mix and country income group, patients undergoing surgery for gastric and colorectal cancer in hospitals with reduced capacities had higher mortality (6.2 vs. 4.0%; P < 0.001), predominantly explained by limited capacity to rescue following the development of major complications (61.3 vs. 72.1%; P < 0.001).

Conclusions

Hospitals with certain system capacities achieve better outcomes following cancer surgery, independent of country-income group. For cancers amenable to surgical treatment, national cancer care plans should include both surgical capacity building and concurrent hospital facility development to maximise reductions in cancer-associated mortality.

Efficacy and safety of a fixed-dose combination of ibuprofen and caffeine in the management of moderate to severe dental pain after third molar extraction

Background

Ibuprofen is an effective analgesic treatment with a ceiling effect at doses above 400 mg. This study compared the combination of ibuprofen 400 mg and caffeine 100 mg with ibuprofen 400 mg monotherapy, caffeine and placebo in the analgesic treatment of moderate to severe acute dental pain following third molar extraction.

Methods

Phase III, active‐/placebo‐controlled, double‐blind, single‐centre, two‐stage, parallel‐group study in adult patients with at least moderate baseline pain intensity. Primary endpoint was defined as the time‐weighted sum of pain relief and pain intensity difference over 8 h (SPRID0–8 h), secondary endpoints included duration of pain relief, time to meaningful pain relief and more.

Results

N = 748 patients were enrolled and N = 562 treated. Mean baseline pain intensity was 7.7 on a 0–10 numerical rating scale. Analysis of SPRID0–8 h demonstrated superior analgesic effects for a single dose of ibuprofen/caffeine versus ibuprofen, caffeine and placebo over 8 h, rescue medication in this stage was requested by more patients on ibuprofen (32.5%) than on ibuprofen/caffeine (16.0%). Median time to meaningful pain relief was shorter for ibuprofen/caffeine (1.13 h) compared with ibuprofen (1.78 h; p = 0.0001). More patients on ibuprofen/caffeine than on ibuprofen reported meaningful pain relief. Adverse events were infrequent and mostly mild or moderate across treatment groups. Tolerability was rated as ‘very good’ or ‘excellent’ by most patients in both treatment groups.

Conclusion

This study demonstrated clinically relevant superiority of ibuprofen/caffeine over monotherapy with ibuprofen in patients with acute dental pain. All treatments were well tolerated.

Significance

This trial showed superior efficacy of 400/100 mg ibuprofen/caffeine, compared to 400 mg ibuprofen alone, for treating acute pain, reflecting that caffeine is an effective analgesic adjuvant. Data on efficacy of 400 mg ibuprofen combined with caffeine for the treatment of acute pain were not available yet.

Topical ambroxol for the treatment of neuropathic pain. An initial clinical observation

BACKGROUND

Neuropathic pain is difficult to treat, and the available options are often inadequate. The expectorant ambroxol also acts as a strong local anaesthetic and blocks sodium channels about 40 times more potently than lidocaine. It preferentially inhibits the channel subtype Nav 1.8, which is expressed especially in nociceptive C-fibres. In view of the low toxicity of ambroxol, it seemed reasonable to try using it for the treatment of neuropathic pain that failed to respond to other standard options.

MATERIAL AND METHODS

The medical records of seven patients with severe neuropathic pain and pain reduction following topical ambroxol treatment are reported retrospectively. As standard therapies had not proved sufficient, a topical ambroxol 20% cream was repeatedly applied by the patients in the area of neuropathic pain.

RESULTS

The reasons for neuropathic pain were postherpetic neuralgia (2 ×), mononeuropathy multiplex, phantom pain, deafferentation pain, postoperative neuralgia and foot neuropathy of unknown origin. The individual mean pain intensity reported was between 4 and 6/10 (NRS), maximum pain at 6-10/10 (NRS). The pain reduction achieved individually following ambroxol cream was 2-8 points (NRS) within 5-30 min and lasted for 3-8 h. Pain attacks were reduced in all five patients presenting with this problem. Four patients with no improvement after lidocaine 5% and one patient with no response to capsaicin 8% nevertheless experienced a pain reduction with topical ambroxol. No patient reported any side effects or skin changes during a treatment that has since been continued for up to 4 years.

CONCLUSION

Ambroxol acts as a strong local anaesthetic and preferentially inhibits the nociceptively relevant sodium channel subtype Nav 1.8. For the first time, we report below on a relevant pain relief following topical ambroxol 20% cream in patients with neuropathic pain. In view of the positive side effect profile, the clinical benefit in patients with pain should be investigated further.

[Topical ambroxol for the treatment of neuropathic pain: A first clinical observation. German version]

BACKGROUND

Neuropathic pain is difficult to treat and available options are frequently not sufficient. The expectorant ambroxol also works as a strong local anesthetic and blocks sodium channels about 40 times more potently than lidocaine. Ambroxol preferentially inhibits the channel subtype Nav 1.8, which is expressed particularly in nociceptive C fibers. Due to the low toxicity, topical ambroxol seemed to represent a reasonable therapeutic attempt for treatment of neuropathic pain resistant to other standard options.

MATERIALS AND METHODS

Medical records of 7 patients with severe neuropathic pain, in whom many attempts at treatment with approved substances were not sufficient or possible, are reported retrospectively. Patients were then treated with topical ambroxol 20% cream applied in the area of neuropathic pain.

RESULTS

Causes of neuropathic pain were postherpetic neuralgia (2-×), mononeuropathy multiplex, phantom pain, deafferentation pain, postoperative neuralgia and an unclear allodynia of the foot. Mean pain intensity was reported as 4-6/10 on a numeric rating scale (NRS) and maximum pain intensity as 6-10/10. Pain reduction following ambroxol cream was 2-8 points (NRS) within 15-30 min and lasted 3-8 h. Pain attacks were reduced in all 5 patients presenting this problem. Topical ambroxol achieved pain reduction in 4 patients with no improvement after lidocaine 5% and 1 patient with no response to capsaicin 8%. No adverse events or skin changes have been observed, and the longest treatment duration is currently 4 years.

CONCLUSION

Ambroxol acts as a strong local anesthetic and preferentially inhibits the nociceptive-relevant sodium channel subtype Nav 1.8. For the first time, we report relevant pain reduction following topical Ambroxol 20% cream in patients with neuropathic pain. Regarding the advantageous profile with rare side effects, the clinical benefit for pain patients should be further investigated.

Efficacy and safety of nicoboxil/nonivamide ointment for the treatment of acute pain in the low back - A randomized, controlled trial

Background

Until now, nonivamide/nicoboxil ointment has not been tested in a randomized trial for the treatment of acute non‐specific low back pain.

Methods

This phase III randomized, double‐blind, active‐ and placebo‐controlled, multi‐centre trial investigated efficacy, safety and tolerability of topical nicoboxil 2.5%/nonivamide 0.4% for treatment of acute non‐specific low back pain [primary endpoint: pain intensity (PI) difference between pre‐dose baseline and 8 h after the first application].

Results

Patients (n = 805), 18–74 years of age were treated for up to 4 days with nicoboxil 2.5%/nonivamide 0.4%, nicoboxil 2.5%, nonivamide 0.4% or placebo ointment. Pre‐dose baseline pain intensity (6.6 on a 0‐ to 10‐point numerical rating scale) was reduced by 1.049 points with placebo, by 1.428 points with nicoboxil, by 2.252 points with nonivamide and by 2.410 points with nicoboxil/nonivamide after 8 h (p < 0.0001 for nicoboxil/nonivamide vs. placebo, nicoboxil; p = 0.4171 for nicoboxil/nonivamide vs. nonivamide). At the end of treatment, the combination provided more pronounced PI reduction (3.540 points) compared with nicoboxil (2.371, p < 0.0001), nonivamide (3.074, p = 0.0259) and placebo (1.884, p < 0.0001). Low back mobility scores on Day 1 were better for the combination compared with all other treatments (p < 0.044); on Day 2–4, scores were better than for placebo and nicoboxil (p < 0.003). Patients assessed efficacy of the combination as greater than of the comparators (p ≤ 0.0129). All treatments were tolerated well. No treatment‐related serious adverse events were reported.

Conclusion

Nicoboxil/nonivamide ointment is an effective, well‐tolerated medication for the treatment of acute non‐specific low back pain.

Effect of hyoscine butylbromide (Buscopan®) on cholinergic pathways in the human intestine

BACKGROUND

Hyoscine butylbromide (HBB, Buscopan(®) ) is clinically used to treat intestinal cramps and visceral pain. Various studies, mainly on animal tissues, suggested that its antimuscarinic action is responsible for its spasmolytic effect. However, functional in vitro studies with human tissue have not been performed so far.

METHODS

We wanted to provide a comprehensive study on the mode of action of HBB in human intestinal samples and investigated HBB (1 nmol L(-1) -10 μmol L(-1)) effects on muscle activity with isometric force transducers and calcium imaging, on epithelial secretion with Ussing chamber technique and on enteric neurons using fast neuroimaging.

KEY RESULTS

Hyoscine butylbromide concentration dependently reduced muscle contractions, calcium mobilization, and epithelial secretion induced by the muscarinic agonist bethanechol with IC50 values of 429, 121, and 224 nmol L(-1), respectively. Forskolin-induced secretion was not altered by HBB. Cholinergic muscarinic muscle and epithelial responses evoked by electrical nerve stimulation were inhibited by 1-10 μmol L(-1) HBB. Moreover, HBB significantly reduced the bethanechol-induced action potential discharge in enteric neurons. Interestingly, we observed that high concentrations of HBB (10 μmol L(-1)) moderately decreased nicotinic receptor-mediated secretion, motility, and nerve activity.

CONCLUSIONS & INFERENCES

The results demonstrated the strong antimuscarinic action of HBB whereas the nicotinic antagonism at higher concentrations plays at most a moderate modulatory role. The muscle relaxing effect of HBB and its inhibition of muscarinic nerve activation likely explain its clinical use as an antispasmodic drug. Our results further highlight a so far unknown antisecretory action of HBB which warrants further clinical studies on its use in secretory disorders.

A label-free, impedance-based real time assay to identify drug-induced toxicities and differentiate cytostatic from cytotoxic effects

Cell-based assays are key tools in drug safety assessment. However, they usually provide only limited information about time-kinetics of a toxic effect and implementing multiple measurements is often complex. To overcome these issues we established an impedance-based approach which is able to differentiate cytostatic from cytotoxic drugs by recording time-kinetics of compound-effects on cells. NIH 3T3 fibroblasts were seeded on xCELLigence® E-plates and impedance was continuously measured over 5 days. The obtained results reflected cytotoxicity and cell proliferation, as confirmed by neutral red uptake in vitro. Based on known toxicants, we established an algorithm able to discriminate cytostatic, cytotoxic and non-toxic compounds based on the shape of the impedance curves. Analyzing impedance curve patterns of additional 37 compounds allowed the identification and differentiation of these distinct effects as results correlated well with previous in vivo findings. We show that impedance-based real-time cell analysis is a convenient tool to characterize and discriminate effects of compounds on cells in a time-dependent and label-free manner. The presented impedance assay could be used to further characterize toxicities observed in vivo or in vitro. Due to the ease of performance it may also be a suitable screening tool.

Effectiveness and safety of topical capsaicin cream in the treatment of chronic soft tissue pain

Topical capsaicin is an established treatment option for various pain conditions. In a randomized double-blind multi-centre study, 281 patients suffering from chronic soft tissue pain were treated either with a cream containing capsaicin 0.05% ('Finalgon® CPDWärmecreme', n = 140) or placebo (n = 141). Of these, 151 were excluded from the ITT analysis, as they had in addition to their soft-tissue pain, pain of other origin. The primary outcome measure was a positive treatment response, defined as a pain sum score reduction of 30% or more. After 3 weeks of treatment, the median pain sum score had decreased by 49% (capsicum group) and 23% (placebo group) (ITT analysis, p = 0.0006). The odds ratio of the responders in favour for capsaicin was 4.3 (CI 97.5% lower limit 1.9, p < 0.0001). Improvements in the secondary efficacy measures confirmed the results. Likewise, all outcome measures had significantly more improved in the capsaicin-treated compared with the placebo-treated chronic back pain sufferers. All patients were included in the safety assessments. More adverse events occurred in the capsicum group (n = 13) than in the placebo group (n = 6). The capsaicin cream was generally well tolerated. The results indicate that capsaicin cream is useful in patients with chronic soft tissue pain and is also efficacious in patients with chronic back pain for which effectiveness was already demonstrated in earlier clinical trials.

In vivo pharmacology of BIIR 561 CL, a novel combined antagonist of AMPA receptors and voltage-dependent Na(+) channels

Glutamate receptors of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) subtype and voltage-gated Na(+) channels are associated with diseases of the central nervous system characterized by neuronal over-excitation as in epilepsy or cerebral ischaemia. In animal models, AMPA receptor antagonists and Na(+) channel blockers provide protection in these conditions. Dimethyl-[2-[2-(3-phenyl-[1,2,4]oxadiazol-5-yl)-phenoxyl]-ethyl]-amine hydrochloride (BIIR 561 CL) combines both, AMPA receptor - and Na(+) channel blocking properties in one molecule. Here, BIIR 561 CL was investigated in vivo. BIIR 561 CL protected mice against AMPA-induced toxicity with an ED(50) value of 4.5 mg kg(-1) following subcutaneous (s.c.) administration. A 0.1% solution of BIIR 561 CL provided local anaesthesia in the corneal reflex test in rabbits. In mice, the compound prevented tonic seizures in the maximal electroshock (MES) model with an ED(50) value of 3.0 mg kg(-1) s.c. In amygdala-kindled rats, BIIR 561 CL inhibited seizures at doses of 3 and 11 mg kg(-1) following intraperitoneal (i.p.) injection. The data show that the combination of blocking AMPA receptor- and voltage-gated Na(+) channels in one molecule induces effective protection in animal models of neuronal over-excitation.

The AMPA receptor/Na(+) channel blocker BIIR 561 CL is protective in a model of global cerebral ischaemia

In this study, we investigated whether the novel neuroprotective compound dimethyl-[2-[2-(3-phenyl-[1,2,4]oxadiazol-5-yl)-phenoxy]-ethyl]-amine hydrochloride, BIIR 561 CL, a combined non-competitive antagonist of AMPA receptors and blocker of voltage-gated Na+ channels, is protective in a rat model of severe global ischaemia. BIIR 561 CL administered immediately after 10 min of ischaemia (occlusion of both carotid arteries plus reduction of arterial blood pressure to 38-40 mm Hg) significantly reduced hippocampal damage at 4 x 26.8 mg/kg (subcutaneous injections). The competitive AMPA receptor antagonist 2,3-dihydro-6-nitro-7-sulfamoyl-benz(F)quinoxaline, NBQX, was used as a reference compound and was protective at 3x30 mg/kg (intraperitoneal and/or subcutaneous administration). BIIR 561 CL significantly reduced the ischaemia-induced premature mortality from 33.6% in the controls to 14.3%, whereas NBQX treatment had no statistically significant effect.Thus, BIIR 561 CL could be shown to reduce hippocampal damage and premature mortality in a model of severe global ischaemia. A compound with these properties might be an interesting candidate for the treatment of disorders related to global cerebral ischaemia in man.

Induction of interleukin-6 by depolarization of neurons

Interleukin-6 (IL-6) has neuromodulatory and neuroprotective effects in vivo. It is expressed in glial cells and neurons both under physiological conditions and in various neurological diseases. Although the expression of IL-6 in glia has been intensely investigated, little is known about the regulation of IL-6 production by neurons. Therefore, we investigated the regulation of IL-6 expression in neurons. Membrane depolarization raised IL-6 mRNA accumulation in primary cortical cells and the PC-12 cell line. In vivo, IL-6 mRNA in the brain increased significantly after epileptic seizures. To investigate IL-6 gene transcription, PC-12 cells were transfected with reporter gene constructs containing the human IL-6 promoter. Membrane depolarization raised IL-6 transcription twofold to fourfold. This increase could be blocked by lowering extracellular Ca(2+) levels or by inhibiting L-type Ca(2+) channels or Ca(2+)/calmodulin-dependent protein kinases. Internal mutations in various elements of the IL-6 promoter revealed the glucocorticoid response element (GRE) 2 to be a depolarization-responsive element. Although the GRE2 bound the glucocorticoid receptor (GR) and was stimulated by dexamethasone, the GR was not responsible for the effect of membrane depolarization because a consensus GRE did not mediate stimulation by membrane depolarization. Instead, another yet undefined factor that binds to the IL-6 GRE2 may mediate the response to membrane depolarization. These data demonstrate that the expression of IL-6 in neurons is regulated by membrane depolarization and suggest a novel Ca(2+)-responsive promoter element. Through this mechanism, IL-6 may function as a neuromodulator induced by neuronal activity.

Characterization of the anticonvulsant and neuroprotectant BIIR 561 CL in vitro: effects on native and recombinant alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors

BIIR 561 CL is a novel blocker of AMPA receptors and voltage-dependent sodium channels. In this study we further describe the effects of BIIR 561 CL on AMPA receptor-mediated membrane currents in rodent neurons, as well as in cells expressing recombinant human GluR1/2 receptors in more detail. BIIR 561 CL suppressed responses to kainate in neuronal cultures from rat cortex with an IC50 of 9.8 microM. Similar effects were observed using acutely dissociated neurons from the CA1 region of rat hippocampus (IC50 = 9.5 microM). Inhibition of kainate responses by BIIR 561 CL was prevented by preapplication of GYKI 53655, suggesting that both non-competitive inhibitors bind to a common site of the receptor. The effect of 10 microM BIIR 561 CL on kainate-induced currents was dependent on extracellular pH, with more pronounced block (84.1%) under acidic conditions (pHextern=6.4), compared to only 30.1% at a pHextern of 8.4. Thus, it can be hypothesized that BIIR 561 CL inhibits AMPA receptors in ischaemic brain regions more effectively than in healthy tissue. BIIR 561 CL inhibited responses to 1 mM glutamate in cells expressing recombinant human GluR1/2 receptors with similar potency, as compared to kainate responses in rat neurons (IC50=17.3 microM). The reference compound NBQX had an IC50 of 25.2 nM. None of the two compounds affected the glutamate-induced receptor desensitization at any tested concentration. The block by BIIR 561 CL was not use-dependent and had fast on- and off-kinetics (tauon=6.8 s; tauoff=1.3 s in hGluR1/2 receptors with 30 microM BIIR 561 CL). Thus, BIIR 561 CL can be anticipated to have a promising profile for the treatment of neurological disorders like brain ischaemia and head trauma.

Effects of the neuropeptide Y Y(2) receptor antagonist BIIE0246 on presynaptic inhibition by neuropeptide Y in rat hippocampal slices

We previously reported that (S)-N(2)-[[1-[2-[4-[(R,S)-5, 11-dihydro-6(6h)-oxodibenz[b, e]azepin-11-yl]-1-piperazinyl]-2-oxoethyl]cylopentyl]a cetyl]-N-[2-[1, 2-dihydro-3,5(4H)-dioxo-1,2-diphenyl-3H-1,2, 4-triazol-4-yl]ethyl]argininamid, BIIE0246, is a potent and highly selective neuropeptide Y Y(2) receptor antagonist. Neuropeptide Y Y(2) receptors have been proposed to mediate the inhibition by neuropeptide Y of excitatory synaptic transmission in rat hippocampus. Therefore, we investigated the effects of BIIE0246 on the electrophysiological properties of neuropeptide Y in rat hippocampal slices and determined the affinity of this novel antagonist for rat hippocampal neuropeptide Y Y(2) receptors. BIIE0246 displayed an affinity of IC(50)=4.0+/-1.6 (n=4) for neuropeptide Y receptor binding sites labelled by 125I-neuropeptide Y in rat hippocampal membranes. At a concentration of 1 microM, BIIE0246 completely antagonized the inhibitory effects of 300 nM neuropeptide Y on synaptic transmission in rat hippocampal slices. This is the first study showing that a selective neuropeptide Y Y(2) receptor antagonist is able to block neuropeptide Y mediated effects in the hippocampus and unambiguously characterizes the presynaptic receptor in the rat hippocampus as the neuropeptide Y Y(2) receptor.

Potent blockade of sodium channels and protection of brain tissue from ischemia by BIII 890 CL

We have synthesized a new benzomorphan derivative, 2R-[2alpha,3(S*), 6alpha]-1,2,3,4,5,6-hexahydro-6,11, 11-trimethyl-3-[2-(phenylmethoxy)propyl]-2, 6-methano-3-benzazocin-10-ol hydrochloride (BIII 890 CL), which displaced [(3)H]batrachotoxinin A-20alpha-benzoate from neurotoxin receptor site 2 of the Na(+) channel in rat brain synaptosomes (IC(50) = 49 nM), but exhibited only low affinity for 65 other receptors and ion channels. BIII 890 CL inhibited Na(+) channels in cells transfected with type IIA Na(+) channel alpha subunits and shifted steady-state inactivation curves to more negative potentials. The IC(50) value for the inactivated Na(+) channel was much lower (77 nM) than for Na(+) channels in the resting state (18 microM). Point mutations F1764A and Y1771A in transmembrane segment S6 in domain IV of the alpha subunit reduced the voltage- and frequency-dependent block, findings which suggest that BIII 890 CL binds to the local anesthetic receptor site in the pore. BIII 890 CL inhibited veratridine-induced glutamate release in brain slices, as well as glutamate release and neurotoxicity in cultured cortical neurons. BIII 890 CL (3-30 mg/kg s.c.) reduced lesion size in mice and rats when administered 5 min after permanent focal cerebral ischemia at doses that did not impair motor coordination. In contrast to many other agents, BIII 890 CL was neuroprotective in both cortical and subcortical regions of the rat brain. Our results demonstrate that BIII 890 CL is a potent, selective, and highly use-dependent Na(+) channel blocker that protects brain tissue from the deleterious effects of focal cerebral ischemia in rodents.

Developmental regulation of AMPA-receptor properties in CA1 pyramidal neurons of rat hippocampus

AMPA-receptor (AMPA-R) currents were recorded from CA1 pyramidal neurons in situ and after acute isolation from the hippocampus of 3- to 45-day-old rats. Membrane currents were analyzed by combining the patch clamp method with fast application techniques. The complete block of receptor currents by GYKI 53655 and the absence of modulation by Concanavalin A indicated that the cells exclusively expressed non-NMDA glutamate receptors of the AMPA subtype while functional kainate receptors could not be detected. The lowest sensitivity to kainate and NBQX was observed at postnatal day (p) 18. These changes might reflect a lower abundance of GluR1 at that developmental stage. A decrease of potentiation of receptor currents by cyclothiazide (CTZ), an acceleration of the recovery from CTZ potentiation and a faster and more complete desensitization of glutamate-evoked currents suggest an up-regulation of flop splice variants with increasing age. These functional data indicate that AMPA-R expression in CA1 pyramidal neurons varies during postnatal development which can be expected to influence the kinetics of synaptic transmission and the excitotoxic vulnerability as well.

Differential interaction of R-mexiletine with the local anesthetic receptor site on brain and heart sodium channel alpha-subunits

Mexiletine is a class I antiarrhythmic drug with neuroprotective effects in models of brain ischemia attributable to inhibition of brain sodium channels. We compared effects of R-mexiletine on wild-type and mutant rat brain (rbIIA) and heart (rh1) sodium channel alpha-subunits transiently expressed in tsA-201 cells. R-mexiletine induced tonic and frequency-dependent block and bound with a 26-fold (brain) or 35-fold (heart) higher affinity to inactivated sodium channels. Affinities of both resting and inactivated channels for R-mexiletine block were approximately 2-fold higher for heart than for brain channels. Mutations in transmembrane segment IVS6 of heart (rhF1762A) and brain (rbF1764A and rbY1771A) channels, which reduce block by other local anesthetics, reduced high-affinity block of inactivated channels and frequency-dependent block of open channels by R-mexiletine and abolished the difference in affinity between brain and heart sodium channels. Unlike previous local anesthetics studied, the strongest effect was observed for mutation rbY1771A. Comparison of mutations of the homologous phenylalanine residue in brain and heart channels showed striking differences in the effects of the mutations. rbF1764A reduced drug block by slowing R-mexiletine binding to inactivated channels, whereas rhF1762A reduced block by increasing the rate of dissociation from inactivated and resting channels. Thus, rbF1764/rhF1762 is a critical determinant of affinity and tissue-specific differences in mexiletine block of brain and heart sodium channels, but its role in drug interaction differs in these two channel isoforms.

Induction of potassium channels in mouse brain microglia: cells acquire responsiveness to pneumococcal cell wall components during late development

Lipopolysaccharides derived from cell walls of Gram-negative bacteria have proven a useful tool to simulate bacterial infection of the central nervous system. Rapid activation of microglia within the brain parenchyma as well as in vitro has thereby been shown to be an early event upon bacterial or lipopolysaccharide challenges. Less is known about microglial responses to a contact with Gram-positive bacteria, such as Streptococcus pneumoniae, a lethal pathogen causing meningitis with a 30% mortality rate. In the present study, we compared lipopolysaccharide-induced microglial activation in vitro with that induced by preparations of pneumococcal cell walls. As a readout of microglial activation, we studied by patch-clamp recording the expression of outward rectifying potassium currents (IK+OR), which are known to be induced by lipopolysaccharide. We found that pneumococcal cell walls and lipopolysaccharide induced a similar type of IK+OR. Stimulation of IK+OR by pneumococcal cell walls and lipopolysaccharide involved protein synthesis since it was not induced in the presence of cycloheximide. Pharmacological characterization of the pneumococcal cell wall- and lipopolysaccharide-induced currents with specific ion channel blockers indicated for both cases expression of the charybdotoxin/margatoxin-sensitive Kv1.3 subtype of the Shaker family of voltage-dependent potassium channels. Activation of the outward currents by pneumococcal cell walls depended on the developmental stage: while lipopolysaccharide triggered IK+OR in both embryonal and postnatal microglial cells, pneumococcal cell walls had only a marginal effect on embryonal cells. This, however, does not imply that embryonic microglial cells are unresponsive to pneumococcal cell walls. In both embryonic and postnatal cells, (i) the amplitude of the constitutively expressed inward rectifying potassium current was significantly reduced, (ii) tumor necrosis factor-a was released and (iii) the cells changed their morphology, similarly as it was induced by lipopolysaccharide treatment. Thus, embryonic microglial cells are sensitive to pneumococcal cell wall challenges, but respond with a distinctly different pattern of physiological reactions. The expression of IK+OR could thus be a suitable tool to study signalling cascades selectively involved in the activation of microglia by Gram-negative and -positive cell wall components and to functionally distinguish between populations of microglial cells.

BIIR 561 CL: a novel combined antagonist of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors and voltage-dependent sodium channels with anticonvulsive and neuroprotective properties

Antagonists of glutamate receptors of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) subtype, as well as of voltage-gated sodium channels, exhibit anticonvulsive and neuroprotective properties in vivo. One can postulate that a compound that combines both principles might be useful for the treatment of disorders of the central nervous system, like focal or global ischemia. Here, we present data on the effects of dimethyl-(2-[2-(3-phenyl-[1,2, 4]oxadiazol-5-yl)-phenoxy]ethyl)-amine hydrochloride (BIIR 561 CL) on neuronal AMPA receptors and voltage-dependent sodium channels. BIIR 561 CL inhibited AMPA receptor-mediated membrane currents in cultured cortical neurons with an IC50 value of 8.5 microM. The inhibition was noncompetitive. In a cortical wedge preparation, BIIR 561 CL reduced AMPA-induced depolarizations with an IC50 value of 10.8 microM. In addition to the effects on the glutamatergic system, BIIR 561 CL inhibited binding of radiolabeled batrachotoxin to rat brain synaptosomal membranes with a Ki value of 1.2 microM. The compound reduced sodium currents in voltage-clamped cortical neurons with an IC50 value of 5.2 microM and inhibited the veratridine-induced release of glutamate from rat brain slices with an IC50 value of 2.3 microM. Thus, BIIR 561 CL inhibited AMPA receptors and voltage-gated sodium channels in a variety of preparations. BIIR 561 CL suppressed tonic seizures in a maximum electroshock model in mice with an ED50 value of 2.8 mg/kg after s.c. administration. In a model of focal ischemia in mice, i.p. administration of 6 or 60 mg/kg BIIR 561 CL reduced the area of the infarcted cortical surface. These data show that BIIR 561 CL is a combined antagonist of AMPA receptors and voltage-gated sodium channels with promising anticonvulsive and neuroprotective properties.

De novo acquisition of neuronal polarity in retinoic acid-induced embryonal carcinoma cells

The mouse embryonal carcinoma cell line PCC7-Mz1 represents an advantageous model to study acquisition of polarity by neurons. During the first two days after differentiation is induced by the addition of retinoic acid, the neuronal derivatives develop extensions which for at least four more days do not differ from each other in growth characteristics, morphology, and marker expression. Beginning around differentiation day 6 and following the relocation of the nucleus from a central to a polar position in the cell soma, the morphology and marker expression changes dramatically: expression of MAP2 diminishes and eventually disappears in the thinner neurite (future axon), which originates at the nucleated pole, but remains strong in the branched, broad based neurite(s). The opposite changes in expression are observed for synaptophysin, together with a clustering of the vesicle protein in varicosity-like areas. Complete segregation of expression of the two markers is achieved around day 12, shortly followed by dendrite-specific location of MAP2 mRNA and the ability to generate and conduct action potentials. Our studies add several aspects to the process of neuronal polarity acquisition, as it was previously studied in primary cultures of embryonic neurons: (i) we monitored neuronal differentiation from the birth of neurons, rather than from later and less defined maturation stages, (ii) cell nucleus relocation may be associated with the induction of neuronal polarity, and (iii) functional competence of neurons is closely associated with previous acquisition of polarity. Acquisition of polarity by PCC7-Mz1 neuronal derivatives probably refers to de novo acquisition rather than to reestablishment of polarity.

The effects of copper ions on glutamate receptors in cultured rat cortical neurons

Copper plays an important role in the function of many physiological processes and can affect different neurotransmitter systems. In this study, we used the patch-clamp technique to investigate the effect of copper ions on glutamate receptors in cultured rat cortical neurons. Cu2+ inhibited (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptors with an IC50 of 4.3 +/- 0.6 microM (with 100 microM kainate, holding potential -60 mV). The concentration-response could be best described by a two-site binding model. Moreover, copper reduced the efficacy of kainate at the AMPA receptor: in the presence of 30 microM Cu2+, the EC50 of kainate was shifted from 100.3 +/- 2.0 microM to 329.9 +/- 31.4 microM. The block by copper ions was not use-dependent. Complete recovery only occurred after the application of a high agonist concentration, or in the presence of the antioxidant dithiotreitol (DTT). A high concentration of histidine, a physiological ligand for Cu2+, did not augment the recovery. The kinetics of block were compared to those induced by 2,3-dihydro-6-nitro-7-sulfamoyl-benz(F)quinoxaline (NBQX), a well-described competitive antagonist of AMPA receptors. The onset, as well as the offset of block by NBQX could be well approximated by single exponential functions with time constants of 0.28 +/- 0.02 and 0.87 +/- 0.09 s, respectively. Within seconds of wash-out of the antagonist, the response to kainate completely recovered. The kinetics of copper block were more complex: the block developed more slowly, and the onset, as well as the offset could be described by two exponential functions with quite different time constants (tau(on1), 0.8 +/- 0.13 s; tau(on2), 8.32 +/- 1.13 s; tau(off1), 0.17 +/- 0.01 s; tau(off2), 69 +/- 36.3 s). In addition to the described effects, Cu2+ also blocked currents induced by the application of N-methyl-D-aspartate (IC50: 15.0 +/- 2.6 microM with 50 microM NMDA). Based on these findings, a modulatory role of copper ions on the neurotransmission by excitatory amino acids is discussed.

Interactions of the dye Evans Blue and GYKI 52466, a 2,3-benzodiazepine, with (S)- alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors in cultured rat cortical neurons: electrophysiological evidence for at least two different binding sites for non-competitive antagonists

The effects of the dye Evans Blue and GYKI 52466, a 2,3-benzodiazepine, on (S)- alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptors in primary cultured rat cortical neurons were investigated using the patch-clamp technique. Evans Blue and GYKI 52466 reduced the currents induced by the application of 100 microM kainate with IC50 values of 10.6 +/- 1.4 microM and 12.1 +/- 0.4 microM, respectively. In contrast to the similar potencies of the two compounds, their kinetics of block were quite different with those of Evans Blue being more complex. The on-, as well as the off-reaction of the block by GYKI 52466 could be described by single exponential functions, whereas two different time-constants for binding and one time-constant for the unbinding of Evans Blue were found. The block of AMPA receptors by Evans Blue was not completely reversible under the experimental conditions applied in this study. GYKI 52466 was not able to augment the recovery after inhibiting AMPA receptors with Evans Blue. Moreover, preapplication of a high concentration of GYKI 52466 did not prevent the inhibition of AMPA receptors by Evans Blue. We therefore conclude that GYKI 52466 and Evans Blue bind to two different sites at AMPA receptors in primary cultured cortical neurons.

Investigations on the mechanism of action of the antiproliferant and ion channel antagonist flufenamic acid

The compound flufenamic acid has been previously described as an inhibitor of chloride- and non-selective cation channels. Moreover, this compound showed antiproliferative effects in the mouse fibroblast cell line LM(TK-). In this study, we investigated the effects of this compound on cell proliferation and membrane currents induced by mitogens (such as fetal calf serum, FCS) or platelet-derived growth factor (PDGF) in LM(TK-) cells. After a brief application of FCS or PDGF (5-15 s), the electrical response of the cells was biphasic: First, a transient potassium conductance was activated, which appeared 8.3 +/- 0.7 s after the onset of stimulation and lasted for 30.1 +/- 2.9 s. The corresponding single channel currents in cell-attached patches had an amplitude of 3-4 pA (at a holding potential of +60 mV). The second effect of serum or PDGF was the occurrence of a cation conductance for monovalent ions (sodium, potassium and cesium) and calcium. In contrast to the potassium current, this conductance activated later (11.8 +/- 1.6 s after onset of fetal calf serum stimulation) and remained activated for minutes. Flufenamic acid inhibited the proliferation of LM(TK-) cells reversibly and in a concentration-dependent manner. This effect can be correlated with the inhibitory effects of flufenamic acid on mitogen-induced membrane currents: The compound inhibited the non-selective cation current with an IC50 of 38 microM, whereas 135 microM were necessary for halfmaximal inhibition of the potassium current; this is very close to the concentration for halfmaximal inhibition of cell proliferation (120 microM). Hence, on the grounds of this comparison the blockade of the non-selective cation current appears to be of only minor importance for the blockade of cell proliferation.

Potassium currents in cultured cells of the rat retinal pigment epithelium

Whole-cell currents were investigated in cultured rat retinal pigment epithelial (RPE) cells. Two voltage-dependent conductances were discriminated. First, at potentials more positive than -30 mV, a time-dependent outward current was activated. Inhibition by Ba2+ (10 mM) and 4-aminopyridine (10 mM) indicated that this current was carried by potassium ions. This current showed no inactivation during 5 sec depolarizations. Second, an inward current, sensitive to Ba2+ (10 mM) and 4-aminopyridine (10 mM), was activated at potentials more negative than -70 mV. Under extra- and intracellular potassium-free conditions, both currents disappeared. In summary, cultured rat RPE cells expressed one potassium conductance similar to the delayed rectifier and one similar to the inward rectifier. The delayed rectifier expressed characteristics comparable with those known in mammalian species and different from those in non-mammalian species.

Voltage- and Ca(2+)-dependence of the K+ channel in the vacuolar membrane of Chenopodium rubrum L. suspension cells

Voltage- and Ca(2+)-dependence of the slow-activating SV-K+ channel in the vacuolar membrane of Chenopodium rubrum suspension cells has been analyzed using the patch clamp technique in the vacuole-attached, outside-out and whole-vacuolar configuration. Patch-pipette perfusion was applied to measure Ca2+ dependence of single channels in the attached-configuration. Using the PCLAMP-software (Axon Instruments), an algorithm was developed to extract reliable individual channel data from multi-channel activity records, including open probability, mean open and closed times, as well as time constants for open and closed distributions. The channel conductance of the major open state was about 83 pS (seal resistance > 8 G omega) at 30 mV (transmembrane voltage Vm, vacuole negative), and symmetrical 100 mM KCl. the channel exhibited a strong voltage- and a weak Ca(2+)-activation: increasing Vm from 40 to 100 mV is equivalent to a Ca2+ concentration change from 10(-7) to 10(-4) M. Mean open probabilities at Vm = 30 mV were 0.03 with 1 microM and 0.09 with 100 microM Ca2+. Mean open times were approx. 7 ms, and almost independent of both, voltage and Ca2+. Mean closed times, however, varied in a strongly voltage- and Ca(2+)-dependent manner, e.g., at Vm = 30 mV dropped from 205 to 67 ms, if Ca2+ was raised from 10(-6) to 10(-4) M. Open and closed distributions of events within bursts could be fitted by the sum of two exponentials with time constants between 0.3 and 11 ms.

Pharmacology of the SV channel in the vacuolar membrane of Chenopodium rubrum suspension cells

Single channel performance and deactivation currents have been analyzed in the presence of cation channel blockers to reveal pharmacological properties of the slow-activating (SV) cation-selective ion channel in the vacuolar membrane (tonoplast) isolated from suspension cells of Chenopodium rubrum L. At a holding potential of -100 mV, the SV channel showed half-maximal inhibition with 20 mM tetraethylammonium (TEA), 7 microM 9-amino-acridine, 6 microM (+)-tubocurarine, 300 nM quinacrine, and 35 microM quinine, respectively. The SV channel is also blocked by charybdotoxin (20 nM at -80 mV) but not by apamine. 9-Amino-acridine, (+)-tubocurarine and quinacrine act in a voltage-dependent fashion, binding to the open channel and to different sites along the transmembrane voltage profile according to Woodhull (J. Gen. Physiol. 61:687-708, 1973). No binding site could be specified for charybdotoxin, which binds to the closed channel, and for quinine. Except for quinine, all tested blockers were effective only if added to the cytoplasmic side of the tonoplast. A structural relationship between the SV channel and Maxi-K channels in animal systems is inferred.

Slowly-activating cation channels in the vacuolar membrane of plants

Among other ion channels and transport proteins, the membrane of plant vacuoles contains a voltage- and calcium-dependent cation channel with activation kinetics in the range of seconds. This SV(= slow vacuolar)-channel has a unit conductance of 60 to 80 pS (in symmetrical 100 mM cation solution) and is strictly inward rectifying. Investigations on the pharmacology of this protein revealed reasonable similarities to calcium-dependent potassium channels of large conductance.

Calmodulin regulates the Ca(2+)-dependent slow-vacuolar ion channel in the tonoplast of Chenopodium rubrum suspension cells

The patch-clamp technique was applied to vacuoles isolated from a photoautotrophic suspension cell culture of Chenopodium rubrum L. and vacuolar clamp currents, which are predominantly carried by the previously identified Ca(2+)-dependent slow vacuolar (SV) ion channels, were recorded. These currents, which were activated by 1-s voltage pulses of -100 mV (vacuolar interior negative) in the presence of 100 μM Ca(2+) (cytosolic side), could be blocked completely and reversibly by the calmodulin antagonist W-7 [N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide] and its chlorine-deficient analogue W-5; half-maximum inhibition was found at approx. 6 μM for W-7 and 70 μM for W-5. Inhibition was reversed by addition of 1 μg · ml(-1) calmodulin purified from Chenopodium cell suspensions; reversal by bovine brain calmodulin was scarcely appreciable. We conclude that cytosolic calmodulin mediates the Ca(2+) dependence of the SV-channel in the Chenopodium tonoplast.

Charybdotoxin blocks cation-channels in the vacuolar membrane of suspension cells of Chenopodium rubrum L

Using the patch-clamp technique, we studied the action of charybdotoxin which blocks Ca(2+)-activated large-conductance K+ channels in animal tissue on the slow-activating (SV), Ca(2+)-activated cation channel in the vacuolar membrane of suspension-cells of Chenopodium rubrum L. The toxin reversibly reduced the vacuolar current with EC50 approximately 20 nM suggesting structural similarities between ion channels in animal and plant membranes.

Biochemical and functional comparison of DNA polymerases alpha, delta, and epsilon from calf thymus

DNA polymerase alpha, delta and epsilon can be isolated simultaneously from calf thymus. DNA polymerase delta was purified to apparent homogeneity by a four-column procedure including DEAE-Sephacel, phenyl-Sepharose, phosphocellulose, and hydroxylapatite, yielding two polypeptides of 125 and 48 kDa, respectively. On hydroxylapatite DNA polymerase delta can completely be separated from DNA polymerase epsilon. By KCl DNA polymerase delta is eluted first, while addition of potassium phosphate elutes DNA polymerase epsilon. DNA polymerases delta and epsilon could be distinguished from DNA polymerase alpha by their (i) resistance to the monoclonal antibody SJK 132-20, (ii) relative resistance to N2-[p-(n-butyl)phenyl]-2-deoxyguanosine triphosphate and 2-[p-(n-butyl)anilino]-2-deoxyadenosine triphosphate, (iii) presence of a 3'----5' exonuclease, (iv) polypeptide composition, (v) template requirements, (vi) processivities on the homopolymer poly(dA)/oligo(dT12-18), and (vii) lack of primase. The following differences of DNA polymerase delta to DNA polymerase epsilon were evident: (i) the independence of DNA polymerase epsilon to proliferating cell nuclear antigen for processivity, (ii) utilization of deoxy- and ribonucleotide primers, (iii) template requirements in the absence of proliferating cell nuclear antigen, (iv) mode of elution from hydroxylapatite, and (v) sensitivity to d2TTP and to dimethyl sulfoxide. Both enzymes contain a 3'----5' exonuclease, but are devoid of endonuclease, RNase H, DNA helicase, DNA dependent ATPase, DNA primase, and poly(ADP-ribose) polymerase. DNA polymerase delta is 100-150 fold dependent on proliferating cell nuclear antigen for activity and processivity on poly(dA)/oligo(dT12-18) at base ratios between 1:1 to 100:1. The activity of DNA polymerase delta requires an acidic pH of 6.5 and is also found on poly(dT)/oligo(dA12-18) and on poly(dT)/oligo(A12-18) but not on 10 other templates tested. All three DNA polymerases can be classified according to the revised nomenclature for eukaryotic DNA polymerases (Burgers, P.M. J., Bambara, R. A., Campbell, J. L., Chang, L. M. S., Downey, K. M., Hübscher, U., Lee, M. Y. W. T., Linn, S. M., So, A. G., and Spadari, S. (1990) Eur. J. Biochem. 191, 617-618).

(+)-Tubocurarine is a potent inhibitor of cation channels in the vacuolar membrane of Chenopodium rubrum L

The effect of the acetylcholine antagonist and channel blocker (+)-tubocurarine on the calcium-dependent slow vacuolar (SV) cation channels in the tonoplast of suspension-cultured cells of Chenopodium rubrum L. was examined using the patch-clamp technique. In whole-vacuolar recordings the drug strongly suppressed the potassium conductance (EC50: 6 microM) and altered the kinetics of channel inactivation. In excised membrane patches (+)-tubocurarine evokes channel-'flickering' without affecting the single-channel conductance (approx. 80 pS).

Efficient production of chicken egg yolk antibodies against a conserved mammalian protein

The egg yolk of immunized chicken is a rich and inexpensive source of specific polyclonal antibodies. In this paper we show that 20-30 micrograms of a highly conserved mammalian protein, as exemplified by proliferating cell nuclear antigen, are sufficient to induce an immune response. Immunoblot analysis revealed that specific antibodies appeared 20 days after immunization, reached a plateau after 30 days, and remained high until at least day 81. A total amount of 4 g immunoglobulin was extracted from 62 eggs of one immunized hen, yielding approximately 130 mg of specific antibodies.