Abnormal thyroid function is common in takotsubo syndrome and depends on two distinct mechanisms: results of a multicentre observational study

BACKGROUND

Several reports have described Takotsubo syndrome (TTS) secondary to thyrotoxicosis. A complex interaction of central and peripheral catecholamines with thyroid homeostasis has been suggested. In this study, we analysed sequential thyroid hormone profiles during the acute phase of TTS.

METHODS

Thyrotropin (TSH), free T4 (FT4) and free T3 (FT3) concentrations were analysed at predefined time points in 32 patients presenting with TTS or acute coronary syndrome (ACS, n = 16 in each group) in a 2-year period in two German university hospitals. Data were compared to age- and sex-matched controls (10 samples, each of 16 subjects), and an unsupervised machine learning (ML) algorithm identified patterns in the hormone signature. Subjects with thyroid disease and patients receiving amiodarone were excluded from follow-up.

RESULTS

Among patients with TTS, FT4 concentrations were significantly higher when compared to controls or ACS. Four subjects (25%) suffered from subclinical or overt thyrotoxicosis. Two additional patients developed subclinical or overt thyrotoxicosis during stay in hospital. In four subjects (25%), FT4 concentrations were increased, despite nonsuppressed TSH concentration, representing an elevated set point of thyroid homeostasis. The thyroid hormone profile was normal in only six patients (38%) presenting with TTS.

CONCLUSION

Abnormal thyroid function is frequent in patients with TTS. Primary hyperthyroidism and an elevated set point of thyroid homeostasis are common in TTS, suggesting a stress-dependent endocrine response or type 2 thyroid allostasis. Thyroid function may be a worthwhile target in treating or preventing TTS.

Systemic inflammatory response after endoscopic surgery of Zenker's diverticulum

Zenker’s diverticulum can be treated with a carbon dioxide laser or linear stapling device. A retrospective study on patients undergoing elective surgery for Zenker`s diverticulum with carbon dioxide laser or stapler was performed to analyse possible differences in inflammatory responses during the postoperative period. Leucocyte counts and C-reactive protein levels in peripheral blood were measured before and on days 1, 2, 3 and 5 after the operation. Statistical analysis was performed using the Mann-Whitney U-test. Of 34 patients, 16 were treated by laser and 18 by stapler. Age, sex ratio and ASA grade did not differ between the groups. Postoperative leukocytosis was significantly milder in the stapler group compared with patients who were treated by carbon dioxide laser. The mean C-reactive protein (CRP) level on day 1, 2 and 3 after surgery was significantly higher in the CO₂ laser group than in the stapler group. Leukocyte counts recovered on day 3 after surgery in both groups while CRP levels did not decline to preoperative levels at day 5 after the operation in either group. No inflammatory complications such as mediastinitis or pneumonia occurred. In conclusion, the inflammatory response in the early period after carbon dioxide laser diverticulotomy of Zenker’s diverticulum is higher than after stapler-assisted surgery of Zenker’s diverticulum.

Calcium channel gating

Tuned calcium entry through voltage-gated calcium channels is a key requirement for many cellular functions. This is ensured by channel gates which open during membrane depolarizations and seal the pore at rest. The gating process is determined by distinct sub-processes: movement of voltage-sensing domains (charged S4 segments) as well as opening and closure of S6 gates. Neutralization of S4 charges revealed that pore opening of CaV1.2 is triggered by a "gate releasing" movement of all four S4 segments with activation of IS4 (and IIIS4) being a rate-limiting stage. Segment IS4 additionally plays a crucial role in channel inactivation. Remarkably, S4 segments carrying only a single charged residue efficiently participate in gating. However, the complete set of S4 charges is required for stabilization of the open state. Voltage clamp fluorometry, the cryo-EM structure of a mammalian calcium channel, biophysical and pharmacological studies, and mathematical simulations have all contributed to a novel interpretation of the role of voltage sensors in channel opening, closure, and inactivation. We illustrate the role of the different methodologies in gating studies and discuss the key molecular events leading CaV channels to open and to close.

Correlation between human ether-a-go-go-related gene channel inhibition and action potential prolongation

BACKGROUND AND PURPOSE

Human ether-a-go-go-related gene (hERG; Kv 11.1) channel inhibition is a widely accepted predictor of cardiac arrhythmia. hERG channel inhibition alone is often insufficient to predict pro-arrhythmic drug effects. This study used a library of dofetilide derivatives to investigate the relationship between standard measures of hERG current block in an expression system and changes in action potential duration (APD) in human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). The interference from accompanying block of Cav 1.2 and Nav 1.5 channels was investigated along with an in silico AP model.

EXPERIMENTAL APPROACH

Drug-induced changes in APD were assessed in hiPSC-CMs using voltage-sensitive dyes. The IC50 values for dofetilide and 13 derivatives on hERG current were estimated in an HEK293 expression system. The relative potency of each drug on APD was estimated by calculating the dose (D150 ) required to prolong the APD at 90% (APD90 ) repolarization by 50%.

KEY RESULTS

The D150 in hiPSC-CMs was linearly correlated with IC50 of hERG current. In silico simulations supported this finding. Three derivatives inhibited hERG without prolonging APD, and these compounds also inhibited Cav 1.2 and/or Nav 1.5 in a channel state-dependent manner. Adding Cav 1.2 and Nav 1.2 block to the in silico model recapitulated the direction but not the extent of the APD change.

CONCLUSIONS AND IMPLICATIONS

Potency of hERG current inhibition correlates linearly with an index of APD in hiPSC-CMs. The compounds that do not correlate have additional effects including concomitant block of Cav 1.2 and/or Nav 1.5 channels. In silico simulations of hiPSC-CMs APs confirm the principle of the multiple ion channel effects.

Analysis of β-Subunit-dependent GABAA Receptor Modulation and Behavioral Effects of Valerenic Acid Derivatives

Valerenic acid (VA)-a β2/3-selective GABA type A (GABAA) receptor modulator-displays anxiolytic and anticonvulsive effects in mice devoid of sedation, making VA an interesting drug candidate. Here we analyzed β-subunit-dependent enhancement of GABA-induced chloride currents (IGABA) by a library of VA derivatives and studied their effects on pentylenetetrazole (PTZ)-induced seizure threshold and locomotion. Compound-induced IGABA enhancement was determined in oocytes expressing α1β1γ2S, α1β2γ2S, or α1β3γ2S receptors. Effects on seizure threshold and locomotion were studied using C57BL/6N mice and compared with saline-treated controls. β2/3-selective VA derivatives such as VA-amide (VA-A) modulating α1β3γ2S (VA-A: Emax = 972 ± 69%, n = 6, P < 0.05) and α1β2γ2S receptors (Emax = 1119 ± 72%, n = 6, P < 0.05) more efficaciously than VA (α1β3γ2S: VA: Emax = 632 ± 88%, n = 9 versus α1β2γ2S: VA: Emax = 721 ± 68%, n = 6) displayed significantly more pronounced seizure threshold elevation than VA (saline control: 40.4 ± 1.4 mg/kg PTZ versus VA 10 mg/kg: 49.0 ± 1.8 mg/kg PTZ versus VA-A 3 mg/kg: 57.9 ± 1.9 mg/kg PTZ, P < 0.05). Similarly, VA's methylamide (VA-MA) enhancing IGABA through β3-containing receptors more efficaciously than VA (Emax = 1043 ± 57%, P < 0.01, n = 6) displayed stronger anticonvulsive effects. Increased potency of IGABA enhancement and anticonvulsive effects at lower doses compared with VA were observed for VA-tetrazole (α1β3γ2S: VA-TET: EC50 = 6.0 ± 1.0 μM, P < 0.05; VA-TET: 0.3 mg/kg: 47.3 ± 0.5 mg/kg PTZ versus VA: 10 mg/kg: 49.0 ± 1.8 mg/kg PTZ, P < 0.05). At higher doses (≥10 mg/kg), VA-A, VA-MA, and VA-TET reduced locomotion. In contrast, unselective VA derivatives induced anticonvulsive effects only at high doses (30 mg/kg) or did not display any behavioral effects. Our data indicate that the β2/3-selective compounds VA-A, VA-MA, and VA-TET induce anticonvulsive effects at low doses (≤10 mg/kg), whereas impairment of locomotion was observed at doses ≥10 mg/kg.

Identification of the putative binding pocket of valerenic acid on GABAA receptors using docking studies and site-directed mutagenesis

Background and Purpose

β2/3‐subunit‐selective modulation of GABA_A receptors by valerenic acid (VA) is determined by the presence of transmembrane residue β2/3N265. Currently, it is not known whether β2/3N265 is part of VA's binding pocket or is involved in the transduction pathway of VA's action. The aim of this study was to clarify the localization of VA's binding pocket on GABA_A receptors.

Experimental Approach

Docking and a structure‐based three‐dimensional pharmacophore were employed to identify candidate amino acid residues that are likely to interact with VA. Selected amino acid residues were mutated, and VA‐induced modulation of the resulting GABA_A receptors expressed in Xenopus oocytes was analysed.

Key Results

A binding pocket for VA at the β⁺/α⁻ interface encompassing amino acid β3N265 was predicted. Mutational analysis of suggested amino acid residues revealed a complete loss of VA's activity on β3M286W channels as well as significantly decreased efficacy and potency of VA on β3N265S and β3F289S receptors. In addition, reduced efficacy of VA‐induced I_GABA enhancement was also observed for α1M235W, β3R269A and β3M286A constructs.

Conclusions and Implications

Our data suggest that amino acid residues β3N265, β3F289, β3M286, β3R269 in the β3 subunit, at or near the etomidate/propofol binding site(s), form part of a VA binding pocket. The identification of the binding pocket for VA is essential for elucidating its pharmacological effects and might also help to develop new selective GABA_A receptor ligands.

Genetic polymorphisms of twelve X-STRs of the investigator Argus X-12 kit and additional six X-STR centromere region loci in an Egyptian population sample

Recently, many researchers have focused on analysis of different X-chromosomal STRs as they bear the potential to efficiently complement the analysis of autosomal and Y-chromosomal STRs in solving special complex kinship deficiency cases. In the current study we examined a sample of 250 unrelated Egyptian males with the Investigator Argus X-12 kit (Qiagen GmbH, Hilden, Germany) which detects 12 X-STR markers distributed over the entire X-chromosome as four closely linked clusters. Microvariant off ladder alleles as well as null alleles have been detected in some loci. Furthermore, discordant results were observed between the Investigator Argus X-12 and the Mentype(®) Argus X-8 kits (Biotype AG, Dresden, Germany). New primers were designed for loci DXS10101, DXS10146 and DXS10148 to correct the allele drop outs observed in these loci with the Investigator Argus X-12 kit. Additionally, DNA sequence analysis revealed the polymorphisms responsible for the allele drop outs. Furthermore, six additional X-STRs (DXS10161, DXS10159, DXS10162, DXS10163, DXS10164 and DXS10165) located in the centromere region at Xp11.21-Xq11.1 were examined in a single multiplex reaction. Allele and haplotype frequencies as well as different forensic statistical parameters of the 18 X-STR loci tested indicated that they are highly informative in different forensic applications in the Egyptian population. However, some modifications still need to be performed on the Investigator Argus X-12 kit before its use in forensic casework is validated.

Methods for quantification of pore-voltage sensor interaction in Ca(V)1.2

Voltage sensors (VSs) initiate the pore opening and closure in voltage-gated ion channels. Here, we propose a technique for estimation of the equilibrium constant of the up- and downward VS movements and rate constants of pore transitions from macroscopic current kinetics. Bell-shaped voltage dependence of the activation/deactivation time constants and Bolzmann distributions of Ca_V1.2 activation were analyzed in terms of a circular four-state (rest, activated, open, deactivated) channel model: both dependencies uniquely constrain the model parameters. Neutralization of gating charges in IS4 or IIS4 only slightly affects the equilibrium constant of VS transition while affecting simultaneously the rate constants of pore opening and closure. The application of our technique revealed that pore mutations on IS6–IVS6 segments induce pronounced shifts of the VS equilibrium between the resting (down) and activated (up) position. Analyzing a channelopathy mutation highlighted that the leftward shift of the activation curve induced by I781T on IIS6 is only partially (35 %) caused by a destabilization of the channel pore but predominantly (65 %) by a shifted VS equilibrium towards activation. The algorithm proposed for CaV1.2 may be applicable for calculating rate constants from macroscopic current kinetics in other voltage-gated ion channels.

The natural history of spinocerebellar ataxia type 1, 2, 3, and 6: a 2-year follow-up study

OBJECTIVE

To obtain quantitative data on the progression of the most common spinocerebellar ataxias (SCAs) and identify factors that influence their progression, we initiated the EUROSCA natural history study, a multicentric longitudinal cohort study of 526 patients with SCA1, SCA2, SCA3, or SCA6. We report the results of the 1- and 2-year follow-up visits.

METHODS

As the primary outcome measure we used the Scale for the Assessment and Rating of Ataxia (SARA, 0-40), and as a secondary measure the Inventory of Non-Ataxia Symptoms (INAS, 0-16) count.

RESULTS

The annual increase of the SARA score was greatest in SCA1 (2.18 ± 0.17, mean ± SE) followed by SCA3 (1.61 ± 0.12) and SCA2 (1.40 ± 0.11). SARA progression in SCA6 was slowest and nonlinear (first year: 0.35 ± 0.34, second year: 1.44 ± 0.34). Analysis of the INAS count yielded similar results. Larger expanded repeats and earlier age at onset were associated with faster SARA progression in SCA1 and SCA2. In SCA1, repeat length of the expanded allele had a similar effect on INAS progression. In SCA3, SARA progression was influenced by the disease duration at inclusion, and INAS progression was faster in females.

CONCLUSIONS

Our study gives a comprehensive quantitative account of disease progression in SCA1, SCA2, SCA3, and SCA6 and identifies factors that specifically affect disease progression.

Trapping and dissociation of propafenone derivatives in HERG channels

BACKGROUND AND PURPOSE

Human ether-a-go-go related gene (HERG) channel inhibitors may be subdivided into compounds that are trapped in the closed channel conformation and others that dissociate at rest. The structural peculiarities promoting resting state dissociation from HERG channels are currently unknown. A small molecule-like propafenone is efficiently trapped in the closed HERG channel conformation. The aim of this study was to identify structural moieties that would promote dissociation of propafenone derivatives.

EXPERIMENTAL APPROACH

Human ether-a-go-go related gene channels were heterologously expressed in Xenopus oocytes and potassium currents were recorded using the two-microelectrode voltage clamp technique. Recovery from block by 10 propafenone derivatives with variable side chains, but a conserved putative pharmacophore, was analysed.

KEY RESULTS

We have identified structural determinants of propafenone derivatives that enable drug dissociation from the closed channel state. Propafenone and four derivatives with 'short' side chains were trapped in the closed channel. Five out of six bulky derivatives efficiently dissociated from the channel at rest. One propafenone derivative with a similar bulk but lacking an H-bond acceptor in this region was trapped. Correlations were observed between molecular weight and onset of channel block as well as between pK(a) and recovery at rest.

CONCLUSION AND IMPLICATIONS

The data show that extending the size of a trapped HERG blocker-like propafenone by adding a bulky side chain may impede channel closure and thereby facilitate drug dissociation at rest. The presence of an H-bond acceptor in the bulky side chain is, however, essential.

Interaction of diltiazem with an intracellularly accessible binding site on Ca(V)1.2

BACKGROUND AND PURPOSE

Diltiazem inhibits Ca_V1.2 channels and is widely used in clinical practice to treat cardiovascular diseases. Binding determinants for diltiazem are located on segments IIIS6, IVS6 and the selectivity filter of the pore forming α₁ subunit of Ca_V1.2. The aim of the present study was to clarify the location of the diltiazem binding site making use of its membrane-impermeable quaternary derivative d-cis-diltiazem (qDil) and mutant α₁ subunits.

EXPERIMENTAL APPROACH

Ca_V1.2 composed of α1, α2-δ and β2a subunits were expressed in tsA-201 cells and barium currents through Ca_V1.2 channels were recorded using the patch clamp method in the whole cell configuration. qDil was synthesized and applied to the intracellular side (via the patch pipette) or to the extracellular side of the membrane (by bath perfusion).

KEY RESULTS

Quaternary derivative d-cis-diltiazem inhibited Ca_V1.2 when applied to the intracellular side of the membrane in a use-dependent manner (59 ± 4% at 300 µM) and induced only a low level of tonic (non-use-dependent) block (16 ± 2% at 300 µM) when applied to the extracellular side of the membrane. Mutations in IIIS6 and IVS6 that have previously been shown to reduce the sensitivity of Ca_V1.2 to tertiary diltiazem also had reduced sensitivity to intracellularly applied qDil.

CONCLUSION AND IMPLICATIONS

The data show that use-dependent block of in Ca_V1.2 by diltiazem occurs by interaction with a binding site accessible via a hydrophilic route from the intracellular side of the membrane.

Valerenic acid derivatives as novel subunit-selective GABAA receptor ligands - in vitro and in vivo characterization

BACKGROUND AND PURPOSE

Subunit-specific modulators of gamma-aminobutyric acid (GABA) type A (GABA(A)) receptors can help to assess the physiological function of receptors with different subunit composition and also provide the basis for the development of new drugs. Valerenic acid (VA) was recently identified as a beta(2/3) subunit-specific modulator of GABA(A) receptors with anxiolytic potential. The aim of the present study was to generate VA derivatives as novel GABA(A) receptor modulators and to gain insight into the structure-activity relation of this molecule.

EXPERIMENTAL APPROACH

The carboxyl group of VA was substituted by an uncharged amide or amides with different chain length. Modulation of GABA(A) receptors composed of different subunit compositions by the VA derivatives was studied in Xenopus oocytes by means of the two-microelectrode voltage-clamp technique. Half-maximal stimulation of GABA-induced chloride currents (I(GABA)) through GABA(A) receptors (EC(50)) and efficacies (maximal stimulation of I(GABA)) were estimated. Anxiolytic activity of the VA derivatives was studied in mice, applying the elevated plus maze test.

KEY RESULTS

Valerenic acid amide (VA-A) displayed the highest efficacy (more than twofold greater I(GABA) enhancement than VA) and highest potency (EC(50)= 13.7 +/- 2.3 microM) on alpha(1)beta(3) receptors. Higher efficacy and potency of VA-A were also observed on alpha(1)beta(2)gamma(2s) and alpha(3)beta(3)gamma(2s) receptors. Anxiolytic effects were most pronounced for VA-A.

CONCLUSIONS AND IMPLICATIONS

Valerenic acid derivatives with higher efficacy and affinity can be generated. Greater in vitro action of the amide derivative correlated with a more pronounced anxiolytic effect in vivo. The data give further confidence in targeting beta(3) subunit containing GABA(A) receptors for development of anxiolytics.

Estimating the efficiency of benzodiazepines on GABA(A) receptors comprising gamma1 or gamma2 subunits

Background and purpose:

Heterologous expression of α1, β2 and γ2S(γ1) subunits produces a mixed population of GABA_A receptors containing α1β2 or α1β2γ2S(γ1) subunits. GABA sensitivity (lower in receptors containing γ1 or γ2S subunits) and the potentiation of GABA-activated chloride currents (I_GABA) by benzodiazepines (BZDs) are dependent on γ2S(γ1) incorporation. A variable γ subunit incorporation may affect the estimation of I_GABA potentiation by BZDs. We propose an approach for estimation of BZD efficiency that accounts for mixed population of α1β2 and α1β2γ2S(γ1) receptors.

Experimental approach:

We investigated the relation between GABA sensitivity (EC₅₀) and BZD modulation by analysing triazolam-, clotiazepam- and midazolam-induced potentiation of I_GABA in Xenopus oocytes under two-microelectrode voltage clamp.

Key results:

Plotting EC₅₀ versus BZD-induced shifts of GABA concentration-response curves (ΔEC₅₀(BZD)) of oocytes injected with different amounts of α1, β2 and γ2S(γ1) cRNA (1:1:1–1:1:10) revealed a linear regression between γ2S(γ1)-mediated reduction of GABA sensitivity (EC₅₀) and ΔEC₅₀(BZD). The slope factors of the regression were always higher for oocytes expressing α1β2γ1 subunit receptors (1.8±0.1 (triazolam), 1.6±0.1 (clotiazepam), 2.3±0.2 (midazolam)) than for oocytes expressing α1β2γ2S receptors (1.4±0.1 (triazolam), 1.4±0.1 (clotiazepam), 1.3±0.1 (midazolam)). Mutant GABA_A receptors (α1β2-R207Cγ2S) with lower GABA sensitivity showed higher drug efficiencies (slope factors=1.1±0.1 (triazolam), 1.1±0.1 (clotiazepam), 1.2±0.1 (midazolam)).

Conclusions and implications:

Regression analysis enabled the estimation of BZD efficiency when variable mixtures of α1β2 and α1β2γ2S(γ1) receptors are expressed and provided new insights into the γ2S(γ1) dependency of BZD action.

State dependent dissociation of HERG channel inhibitors

BACKGROUND AND PURPOSE

Inhibition of HERG channels prolongs the ventricular action potential and the QT interval with the risk of torsade de pointes arrhythmias and sudden cardiac death. Many drugs induce greater inhibition of HERG channels when the cell membrane is depolarized frequently. The dependence of inhibition on the pulsing rate may yield different IC(50) values at different frequencies and thus affect the quantification of HERG channel block. We systematically compared the kinetics of HERG channel inhibition and recovery from block by 8 blockers at different frequencies.

EXPERIMENTAL APPROACH

HERG channels were expressed heterologously in Xenopus oocytes and currents were measured with the two-electrode voltage clamp technique.

KEY RESULTS

Frequency-dependent block was observed for amiodarone, cisapride, droperidol and haloperidol (group 1) whereas bepridil, domperidone, E-4031 and terfenadine (group 2) induced similar pulse-dependent block at all frequencies. With the group 1 compounds, HERG channels recovered from block in the presence of drug (recovery being voltage-dependent). No substantial recovery from block was observed with the second group of compounds. Washing out of bepridil, domperidone, E-4031 and terfenadine was substantially augmented by frequent pulsing. Mutation D540K in the HERG channel (which exhibits reopening at negative voltages) facilitated recovery from block by these compounds at -140 mV.

CONCLUSION AND IMPLICATIONS

Drug molecules dissociate at different rates from open and closed HERG channels ('use-dependent' dissociation). Our data suggest that apparently 'trapped' drugs (group 2) dissociated from the open channel state whereas group 1 compounds dissociated from open and resting states.

Valerenic acid potentiates and inhibits GABA(A) receptors: molecular mechanism and subunit specificity

Valerian is a commonly used herbal medicinal product for the treatment of anxiety and insomnia. Here we report the stimulation of chloride currents through GABA(A) receptors (I(GABA)) by valerenic acid (VA), a constituent of Valerian. To analyse the molecular basis of VA action, we expressed GABA(A) receptors with 13 different subunit compositions in Xenopus oocytes and measured I(GABA) using the two-microelectrode voltage-clamp technique. We report a subtype-dependent stimulation of I(GABA) by VA. Only channels incorporating beta(2) or beta(3) subunits were stimulated by VA. Replacing beta(2/3) by beta(1) drastically reduced the sensitivity of the resulting GABA(A) channels. The stimulatory effect of VA on alpha(1)beta(2) receptors was substantially reduced by the point mutation beta(2N265S) (known to inhibit loreclezole action). Mutating the corresponding residue of beta(1) (beta(1S290N)) induced VA sensitivity in alpha(1)beta(1S290N) comparable to alpha(1)beta(2) receptors. Modulation of I(GABA) was not significantly dependent on incorporation of alpha(1), alpha(2), alpha(3) or alpha(5) subunits. VA displayed a significantly lower efficiency on channels incorporating alpha(4) subunits. I(GABA) modulation by VA was not gamma subunit dependent and not inhibited by flumazenil (1 microM). VA shifted the GABA concentration-effect curve towards lower GABA concentrations and elicited substantial currents through GABA(A) channels at > or = 30 microM. At higher concentrations (> or = 100 microM), VA and acetoxy-VA inhibit I(GABA). A possible open channel block mechanism is discussed. In summary, VA was identified as a subunit specific allosteric modulator of GABA(A) receptors that is likely to interact with the loreclezole binding pocket.

X chromosomal and autosomal loss of heterozygosity and microsatellite instability in human cervical carcinoma

The study analyzes tumor material and normal tissue from 27 patients with pure squamous cell carcinoma of the uterine cervix for loss of heterozygosity (LOH) and microsatellite instability (MSI) on 14 autosomal and 11 X chromosomal loci. Overall, 4-40% of the informative cases showed LOH at autosomal regions with the highest frequency at 3p (21-40%) and a marked frequency at 2q35-q37.1 (12.5%) and 17p13.3 (10%), representing regions with putative tumor suppressor gene (TSG) function. The frequency of X chromosomal LOH ranged from 4% to 20%, with a maximum at Xq28 (20%) and Xq11.2-q12 (17%), again indicating alterations in TSG. A 12% LOH was seen at Xq21.33-q22.3, a region encoding a protein with a regulatory function in the cell cycle via cyclin-dependent kinases. MSI was detected in autosomal regions in up to 7% in regions linked to the X chromosome in up to 11%, probably indicating alterations of mismatch repair mechanisms. Our results and those obtained from the literature suggest that autosomal LOH and MSI in carcinomas of the cervix uteri are predominantly found at regions with putative TSG function. Beside TSG alterations, X chromosomal LOH is probably more strongly connected to disturbances in cell cycle regulation.

Automated fast perfusion of Xenopus oocytes for drug screening

Fast ('concentration jump') applications of neurotransmitters are crucial for screening studies on ligand-gated ion channels. In this paper, we describe a method for automated fast perfusion of neurotransmitters (or drugs) during two-microelectrode voltage-clamp experiments on Xenopus oocytes. The oocytes are placed in a small bath chamber that is covered by a glass plate with two channels for the microelectrodes that are surrounded by a quartz funnel serving as a reservoir for test solutions. The oocytes are perfused in a vertical direction via the two channels in the plate. Automation of compound delivery is accomplished by means of a programmable pipetting workstation. A mean rise time for 10-90% current increase through muscle-type nACh channels of 55.0+/-1.3 ms (30 muM acetylcholine) was estimated. Automation, fast perfusion rates, and economical use of compounds ( approximately 100 mul/data point) make the system suitable for screening studies on ligand- and voltage-gated ion channels.

X chromosomal and autosomal loss of heterozygosity and microsatellite instability in human cervical carcinoma

The study analyzes tumor material and normal tissue from 27 patients with pure squamous cell carcinoma of the uterine cervix for loss of heterozygosity (LOH) and microsatellite instability (MSI) on 14 autosomal and 11 X chromosomal loci. Overall, 4–40% of the informative cases showed LOH at autosomal regions with the highest frequency at 3p (21–40%) and a marked frequency at 2q35-q37.1 (12.5%) and 17p13.3 (10%), representing regions with putative tumor suppressor gene (TSG) function. The frequency of X chromosomal LOH ranged from 4% to 20%, with a maximum at Xq28 (20%) and Xq11.2-q12 (17%), again indicating alterations in TSG. A 12% LOH was seen at Xq21.33-q22.3, a region encoding a protein with a regulatory function in the cell cycle via cyclin-dependent kinases. MSI was detected in autosomal regions in up to 7% in regions linked to the X chromosome in up to 11%, probably indicating alterations of mismatch repair mechanisms. Our results and those obtained from the literature suggest that autosomal LOH and MSI in carcinomas of the cervix uteri are predominantly found at regions with putative TSG function. Beside TSG alterations, X chromosomal LOH is probably more strongly connected to disturbances in cell cycle regulation.

Pharmacological properties of GABAA receptors containing gamma1 subunits

GABA(A) receptors composed of alpha(1), beta(2), gamma(1) subunits are expressed in only a few areas of the brain and thus represent interesting drug targets. The pharmacological properties of this receptor subtype, however, are largely unknown. In the present study, we expressed alpha(1)beta(2)gamma(1)-GABA(A) receptors in Xenopus laevis oocytes and analyzed their modulation by 21 ligands from 12 structural classes making use of the two-microelectrode voltage-clamp method and a fast perfusion system. Modulation of GABA-induced chloride currents (I(GABA)) was studied at GABA concentrations eliciting 5 to 10% of the maximal response. Triazolam, clotiazepam, midazolam, 2-(4-methoxyphenyl)-2,3,5,6,7,8,9,10-octahydro-cyclohepta-(b)pyrazolo[4,3-d]pyridin-3-one (CGS 20625), 2-(4-chlorophenyl)-pyrazolo[4,3-c]quinolin-3-one (CGS 9896), diazepam, zolpidem, and bretazenil at 1 microM concentrations were able to significantly (>20%) enhance I(GABA) in alpha(1)beta(2)gamma(1) receptors. Methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate, 3-methyl-6-[3-trifluoromethyl-phenyl]-1,2,4-triazolo[4,3-b]pyridazine (Cl 218,872), clobazam, flumazenil, 5-(6-ethyl-7-methoxy-5-methylimidazo[1,2-a]pyrimidin-2-yl)-3-methyl-[1,2,4]-oxadiazole (Ru 33203), 2-phenyl-4-(3-ethyl-piperidinyl)-quinoline (PK 9084), flurazepam, ethyl-7-methoxy-11,12,13,13a-tetrahydro-9-oxo-9H-imidazo[1,5-a]pyrrolo[2,1-c] [1,4]benzodiazepine-1-carboxylate (l-655,708), 2-(6-ethyl-7-methoxy-5-methylimidazo[1,2-a]pyrimidin-2-yl)-4-methyl-thiazole (Ru 33356), and 6-ethyl-7-methoxy-5-methylimidazo[1,2-a]pyrimidin-2-yl)phenylmethanone (Ru 32698) (1 microM each) had no significant effect, and flunitrazepam and 2-phenyl-4-(4-ethyl-piperidinyl)-quinoline (PK 8165) inhibited I(GABA). The most potent compounds triazolam, clotiazepam, midazolam, and CGS 20625 were investigated in more detail on alpha(1)beta(2)gamma(1) and alpha(1)beta(2)gamma(2S) receptors. The potency and efficiency of these compounds for modulating I(GABA) was smaller for alpha(1)beta(2)gamma(1) than for alpha(1)beta(2)gamma(2S) receptors, and their effects on alpha(1)beta(2)gamma(1) could not be blocked by flumazenil. CGS 20625 displayed the highest efficiency by enhancing at 100 microM I(GABA) (alpha(1)beta(2)gamma(2)) by 775 +/- 17% versus 526 +/- 14% I(GABA) (alpha(1)beta(2)gamma(1)) and 157 +/- 17% I(GABA) (alpha(1)beta(2)) (p < 0.05). These data provide new insight into the pharmacological properties of GABA(A) receptors containing gamma(1) subunits and may aid in the design of specific ligands for this receptor subtype.

Stammzelltherapie der Harninkontinenz

Experimental and clinical studies investigated whether urinary incontinence can be effectively treated with transurethral ultrasound-guided injections of autologous myoblasts and fibroblasts.This new therapy was performed in eight female pigs. It could be shown that the injected cells survived well and that new muscle tissue was formed. Next, 42 patients (29 women, 13 men) suffering from urinary stress incontinence were treated. The fibroblasts were mixed with a small amount of collagen as carrier material and injected into the urethral submucosa to treat atrophies of the mucosa. The myoblasts were directly injected into the rhabdosphincter to reconstruct the muscle and to heal morphological and functional defects. In 35 patients urinary incontinence could be completely cured. In seven patients who had undergone multiple surgical procedures and radiotherapy urinary incontinence improved. No side effects or complications were encountered postoperatively. The experimental as well as the clinical data clearly demonstrate that urinary incontinence can be treated effectively with autologous stem cells. The present data support the conclusion that this new therapeutic concept may represent a very promising treatment modality in the future.

A comparative study of three different biomaterials in the engineering of skeletal muscle using a rat animal model

Defects caused by traumatic or postsurgical loss of muscle mass may result in severe impairments of the functionality of skeletal muscle. Tissue engineering represents a possible approach to replace the lost or defective muscle. The aim of this study was to compare the suitability of three different biomaterials as scaffolds for rat myoblasts, using a new animal model. PKH26-fluorescent-stained cultured rat myoblasts were either seeded onto polyglycolic acid meshes or, alternatively, suspended in alginate or in hyaluronic acid-hydrogels. In each of the eight Fisher CDF-344 rats, four capsule pouches were induced by subcutaneous implantation of four silicone sheets. After two weeks the silicone sheets were removed and myoblast-biomaterial-constructs were implanted in the preformed capsules. Specimens were harvested after four weeks and examined histologically by H&E-staining and fluorescence microscopy. All capsules were well-vascularized. Implanted myoblasts fused by forming multinucleated myotubes. This study demonstrates that myoblasts seeded onto different biomaterials can be successfully transplanted into preformed highly vascularized capsule pouches. Our animal model has paved the way for studies of myoblast-biomaterial transplantations into an ectopic non-muscular environment.

On the fate of skeletal myoblasts in a cardiac environment: down-regulation of voltage-gated ion channels

We have analysed the voltage-gated ion channels and fusion competence of skeletal muscle myoblasts labelled with green fluorescent protein (GFP) and the membrane dye PKH transplanted into the infarcted myocardium of syngenic rats. After cell transplantation the animals were killed and GFP(+)-PKH(+) myoblasts enzymatically isolated for subsequent studies of ionic currents through voltage-gated sodium, calcium and potassium channels. A down-regulation of all three types of ion channels after engraftment was observed. The fraction of cells with calcium (68%) and sodium channels (65%) declined to zero within 24 h and 1 week, respectively. Down-regulation of potassium currents (90% in control) occurred within 2 weeks to about 30%. Before injection myoblasts expressed predominantly transient outward potassium channels whereas after isolation from the myocardium exclusively rapid delayed rectifier channels. The currents recovered completely between 1 and 6 weeks under cell culture conditions. The down-regulation of ion channels and changes in potassium current kinetics suggest that the environment provided by infarcted myocardium affects expression of voltage-gated ion channels of skeletal myoblasts.

Combined transplantation of skeletal myoblasts and bone marrow stem cells for myocardial repair in rats

OBJECTIVES

To prove whether intramyocardial transplantation of combined skeletal myoblasts (SM) and mononuclear bone marrow stem cells is superior to the isolated transplantation of these cell types after myocardial infarction in rats.

METHODS

In 67 male Fischer rats myocardial infarction was induced by direct ligature of the LAD. Seven days postinfarction baseline echocardiography and intramyocardial cell transplantation were performed. Via lateral thoracotomy 200 microl containing either 10(7) SMs or 10(7) bone marrow-derived mononuclear cells (BM-MNC) or a combination of 5x10(6) of both cell types (MB) were injected in 10-15 sites in and around the infarct zone. In controls (C) 200 microl of cell-free medium were injected in the same manner. Before injection both cell types were stained using a fluorescent cell linker kit (PKH, Sigma). In addition, SMs were transfected with green fluorescent protein. Nine weeks postinfarction follow-up echocardiography was performed and animals were sacrificed for further analysis.

RESULTS

At baseline echocardiography there was no difference in left ventricular ejection fraction (LVEF; C, SM, BM-MNC, MB: 60.1+/-3.2, 53.3+/-10.2, 53.1+/-8.7, 49+/-9.0%) and left ventricular end diastolic diameter (LVEDD; C, SM, BM-MNC, MB: 6.5+/-0.8, 5.17+/-0.8, 5.77+/-1.4, 6.25+/-0.8 mm) between the different therapeutic groups. Eight weeks after cell transplantation LVEDD was significantly increased in all animals except those that received a combination of myoblasts and bone marrow stem cells (MB; C, SM, BM-MNC, MB: 7.7+/-0.6 mm, P=0.001; 7.7+/-1.5 mm, P<0.001; 7.7+/-1.1 mm, P=0.005; 6.6+/-1.7 mm, P=0.397. At the same time LVEF decreased significantly in the control group (C), stayed unchanged in animals that received bone marrow stem cells (BM-MNC) and increased in animals that received myoblasts (SM) and a combination of both cell types (MB; C, SM, BM-MNC, MB: 45.3+/-7.0%, P=0.05; 63.9+/-15.4%, P=0.044; 54.3+/-6.3%, P=0.607; 63.0+/-11.5%, P=0.039).

CONCLUSIONS

The present data show that the concept of combining SMs with bone marrow-derived stem cells may be of clinical relevance by merging the beneficial effects of each cell line and potentially reducing the required cell quantity. Further studies are required to identify the exact mechanisms underlying this synergy and to allow full exploitation of its therapeutic potential.