Encapsulation and release of α-chymotrypsin from poly(glycerol adipate-co-ω-pentadecalactone) microparticles

Polymer-based microparticles are increasingly becoming of interest for a variety of applications including drug delivery. Recently poly(glycerol adipate) (PGA) and poly(glycol adipate-co-ω-pentadecalactone) have shown promise for delivery of dexamethasone phosphate and ibuprofen. In this paper the copolyester poly(glycol adipate-co-ω-pentadecalactone) was evaluated as a colloidal delivery system for encapsulated therapeutic proteins. Enzyme containing microparticles were prepared via the double water-in-oil-in-water (w/o/w) emulsion-solvent evaporation methodology. α-Chymotrypsin was used as a model proteolytic enzyme and its transfer was monitored during the emulsification process, in addition to in vitro release from formed particles. On average, 22.1 µg protein per 1 mg polymer was encapsulated, although gradual loss of activity of the protein, once released, was recorded. The work presented shows the potential of this polyester as a delivery system for enzymes via microparticles, with improvements to the system achievable via polymer and process optimization. The pendant hydroxyl groups on the polymer backbone provide future capacity for tailored alteration of the physical and chemical properties of the polymer, in addition to covalent attachment of various compounds.     

Modulation of N-methyl-d-aspartate (NMDA)-stimulated noradrenaline release in rat brain cortex by presynaptic α2-adrenoceptors

Summary Rat brain cortex slices and synaptosomes preincubated with [³H]noradrenaline were used to investigate whether the NMDA-evoked noradrenaline release is modulated by agonists or antagonists at presynaptic ₂-adrenoceptors.In experiments on slices, noradrenaline and the preferential ₂-adrenoceptor agonists talipexole (former B-HT 920) and clonidine inhibited the NMDA evoked tritium overflow whereas the selective ₁-adrenoceptor agonists cirazoline and methoxamine were ineffective. The ₂-adrenoceptor antagonists rauwolscine and idazoxan facilitated the NMDA-evoked tritium overflow whereas the preferential ₁-adrenoceptor antagonist prazosin was ineffective. The concentration-response curve of talipexole for its inhibitory effect on NMDA-evoked overflow was shifted to the right by idazoxan (apparent pA₂ = 7.5). The EC₅₀ of NMDA (97 mol/l) for its stimulating effect on tritium overflow was not substantially changed by blockade of ₂-autoreceptors with 1 mol/l rauwolscine (EC₅₀ of NMDA in the presence of the ₂-adrenoceptor antagonist, 155 mol/l), but the maximal overflow of tritium was increased 2.5 fold by this rauwolscine concentration. In experiments on synaptosomes, talipexole and noradrenaline inhibited the NMDA-evoked tritium overflow. The inhibitory effect of talipexole was abolished by idazoxan which, given alone, was ineffective, as was prazosin. Talipexole did also not produce an inhibition when tritium overflow was evoked by NMDA in the presence of -conotoxin GVIA 0.1 mol/l; the latter, by itself, decreased the response to NMDA by about 55%. It is concluded that the NMDA-evoked noradrenaline release in the cerebral cortex is modulated via presynaptic ₂-adrenoceptors on the noradrenergic neurones. Stimulation of these autoreceptors in slices by endogenous noradrenaline does not result in a decreased potency of NMDA, but in a decreased maximum effect, in stimulating noradrenaline release. The inhibitory effect of ₂-adrenoceptor agonists on the NMDA-evoked release is at least partially due to a functional interaction between the NMDA receptors and ₂-autoreceptors at the level of the same varicosities. The results obtained with -conotoxin GVIA suggest that Ca²⁺ influx via the N-type voltage-sensitive calcium channel (VSCC) occurs in response to NMDA receptor stimulation and contributes substantially to the induction of NMDA-evoked noradrenaline release. The inhibitory effect of ₂-adrenoceptor stimulation on this release appears to be ultimately due to an inhibition of the influx of Ca²⁺ via the N-type VSCC. Correspondence to: M. Göthert at the above address     

The 5-HT3 receptor agonist 1-(m-chlorophenyl)-biguanide facilitates noradrenaline release by blockade of α2-adrenoceptors in the mouse brain cortex

We analyzed the facilitatory effect of the 5-HT₃ receptor agonist 1-(m-chlorophenyl)-biguanide (mCPBG) on the electrically evoked noradrenaline release in superfused mouse brain tissue. In addition, we determined the affinities of mCPBG and two other 5-HT receptor ligands, namely, 2-methyl-5-hydroxytryptamine (2-methyl-5-HT; also a 5-HT₃ receptor agonist) and 5-carboxamidotryptamine (5-CT; a 5-HT₁ receptor agonist) for ₂ binding sites. The latter two 5-HT receptor agonists were included because of the claimed involvement of ₂-adrenoceptors in their effects on noradrenaline release.In superfusion experiments on mouse brain cortex slices preincubated with ³H-noradrenaline, tritium overflow evoked by 2-min periods of electrical field stimula tion (3 Hz) was facilitated by mCPBG and, in addition, by rauwolscine (₂-adrenoceptor antagonist) and tetraethylammonium (K⁺ channel blocker) (which were examined for comparison). The effect of mCPBG was not affected by the 5-HT3 receptor antagonist tropisetron or by desipramine but was abolished by rauwolscine. In slices superfused with medium containing desipramine, the concentration-response curve of unlabelled noradrenaline for its inhibitory effect on the electrically (0.3 Hz) evoked overflow was shifted to the right by mCPBG and rauwolscine (apparent pA₂ 5.35 and 7.88, respectively). In another series of superfusion experiments, 4 electrical pulses, administered at 100 Hz, were used to evoke tritium overflow. Tritium overflow evoked by this stimulation procedure (under which an endogenous tone of noradrenaline does not develop) was not affected by mCPBG and rauwolscine but still increased by tetraethylammonium. The specific binding of 3H-rauwolscine to rat brain cortex homogenates was displaced monophasically by unlabelled rauwolscine, mCPBG, 2-methyl-5-HT and 5-CT (pK_i 8.59, 5.84, 5.05 and 5.86, respectively).In conclusion the present results indicate that mCPBG acts as a low-affinity antagonist at ₂-adrenoceptors. This property has to be considered in functional studies of 5-HT₃ receptor-mediated effects in tissues containing ₂-adrenoceptors as well.Abbreviations mCPBG 1-(m-chlorophenyl)-biguanide - 5-CT 5-carboxamidotryptamine - 2-methyl-5-HT 2-methyl-5-hydroxytryptamine - POP pseudo-one-pulse - TEA tetraethylammonium Correspondence to: E. Schlicker at the above address     

Microencapsulation of maltogenic α-amylase in poly(urethane–urea) shell: inverse emulsion method

Abstract

The novel poly(urethane–urea) microcapsules (PUUMC) were obtained by the interfacial polyaddition reaction between the oil-soluble hexamethylene diisocyanate (HMDI) and the water soluble poly(vinyl alcohol) (PVA) in a water-in-oil (W/O) emulsion. The PVA was used instead of diols. Maltogenase L (maltogenic α-amylase from Bacillus stearothermophilus (E. C. 3.2.1.133) (MG) was encapsulated in the PUUMC during or after formation of capsules. The PUUMC were thoroughly characterised by chemical analytical methods, FT-IR, SEM, thermal analysis, surface area, pore volume and size analysis. Furthermore, by carefully analysing the influencing factors including: catalyst and surfactants and their concentrations, the initial molar ratio of PVA and HMDI, stirring rate and ratio of dispersed phase to external phase, the optimum synthesis conditions were found out. A controlled release of MG could be observed in many cases. Delayed-release capsules were obtained when initial concentration of HMDI was increased. These capsules have potential application in biotechnology for saccharification of starch.     

Migration of marrow stromal cells in response to sustained release of stromal-derived factor-1α from poly(lactide ethylene oxide fumarate) hydrogels

Stromal derived factor-1α (SDF-1α) is an important chemokine in stem cell trafficking and plays a critical role in the homing of bone marrow stromal (BMS) cells. However, its use in tissue regeneration is limited by its relatively short half-life and the time-dependent nature of cell homing to the site of injury. The objective of this work was to investigate the release characteristics of SDF-1α from degradable poly(lactide ethylene oxide fumarate) (PLEOF) hydrogels and to determine the effect of sustained release of SDF-1α on migration of BMS cells. Three PLEOF hydrogels with poly(l-lactide) (PLA) fractions of 6%, 9%, and 24% by weight were synthesized. After the addition of chemokine, the polymerizing mixture was crosslinked to produce SDF-1α loaded PLEOF hydrogels. The hydrogels were characterized with respect to sol fraction, water uptake, degradation, SDF-1α loading efficiency and release kinetics, and migration rate of bone marrow stromal (BMS) cells. The more hydrophilic hydrogels with 6% and 9% PLA fraction had a pronounced burst release followed by a period of sustained release by diffusion for 21 days. The more hydrophobic hydrogel with 24% PLA fraction had a less pronounced burst release and displayed a slow but constant release by diffusion between days 1 and 9 followed by a fast release by diffusion-degradation from days 9 to 18. The fraction of active SDF-1α released from 6%, 9%, and 24% hydrogels after 21 days was 34.3%, 32.3%, and 35.8%, respectively. The migration of BMS cells in response to time-released SDF-1α closely followed the protein release kinetics from the hydrogels. The biodegradable PLEOF hydrogel may potentially be useful as a delivery matrix for sustained release of SDF-1α in the proliferative phase of healing for recruitment of progenitor cells in tissue engineering applications.     

Facilitation of serotonin (5-HT) release in the rat brain cortex by cAMP and probable inhibition of adenylate cyclase in 5-HT nerve terminals by presynaptic α2-adrenoceptors

Summary Stimulation-evoked tritium overflow was examined in superfused rat brain cortex slices (stimulus: electrical impulses; 3 Hz) and synaptosomes (stimulus: potassium 12 mmol/l) preincubated with ³H-5-HT. 1. In slices and synaptosomes, the evoked ³H overflow was facilitated by forskolin and 8-Br-cAMP, but was not affected by AH 21-132 (an inhibitor of cAMP phosphodiesterase; cis-6-(p-acetamidophenyl)-1, 2, 3, 4, 4 a,10b-hexahydro-8, 9-dimethoxy-2-methylbenzo [c] [1,6]-naphthyridine). In the presence of AH 21-132, the facilitatory effect of forskolin on evoked overflow was increased. 2. In slices, AH 21-132 or combined administration of forskolin plus AH 21-132 did not change the percentage of basal or evoked ³H overflow represented by unmetabolized ³H-serotonin (about 30% and 60%, respectively). 3. In slices, cocaine or 6-nitroquipazine, an inhibitor of serotonin uptake, did not influence the increase in evoked overflow produced by forskolin plus AH 21-132. Forskolin plus AH 21-132 did not alter the inhibitory effect of serotonin (examined in the presence of 6-nitroquipazine) and the facilitatory effect of metitepin (a serotonin receptor antagonist) on evoked ³H overflow, but considerably decreased the inhibitory effect of clonidine or B-HT 920 (2-amino-6-allyl-5,6,7,8-tetrahydro-4H-thiazolo-[5,4-d]-azepine). The present results suggest that the serotoninergic nerve terminals in the rat brain cortex are endowed with an adenylate cyclase, which is negatively coupled to the presynaptic ₂-adrenoceptors, but is not linked to the presynaptic autoreceptors.This study was supported by a grant of the Deutsche Forschungsgemeinschaft. Part of the present results was reported at the 9th International Congress of Pharmacology, London 1984 (Schlicker et al. 1984) Send offprint requests to M. Göthert     

α(1D)-Adrenoceptor regulates the vasopressor action of α(1A)-adrenoceptor in mesenteric vascular bed of α(1D)-adrenoceptor knockout mice

1 The pressor action of the α(1A)-adrenoceptor (α(1A)-AR) agonist A61603 (N-[5-(4,5-dihydro-1H-imidazol-2-yl)-2-hydroxy-5,6,7,8-tetrahydronaphthalen-1-yl] methanesulfonamide) and the α(1)-ARs agonist phenylephrine and their blockade by selective α(1)-ARs antagonists in the isolated mesenteric vascular bed of wild-type (WT) mice and α(1D)-AR knockout (KO α(1D)-AR) mice were evaluated. 2 The apparent potency of A61603 to increase the perfusion pressure in the mesenteric vascular bed of WT and KO α(1D)-AR mice is 86 and 138 times the affinity of phenylephrine, respectively. 3 A61603 also enhanced the perfusion pressure by ≈1.7 fold in the mesenteric vascular bed of WT mice compared with KO α(1D)-AR mice. 4 Because of its high affinity, low concentrations of the α(1A)-AR selective antagonist RS100329 (5-methyl-3-[3-[4-[2-(2,2,2,-trifluoroethoxy) phenyl]-1-piperazinyl] propyl]-2,4-(1H)-pyrimidinedione) shifted the agonist concentration-response curves to the right in the mesenteric vascular bed of WT and KO α(1D)-AR mice. 5 The α(1D)-AR selective antagonist BMY7378 (8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4.5] decane-7,9-dione) did not modify the A61603 or the phenylephrine-induced pressor effect. 6 The α(1B/D)-ARs alkylating antagonist chloroethylclonidine (CEC) shifted the agonist concentration-response curves to the right and decreased the maximum phenylephrine-induced vascular contraction in KO α(1D)-AR mice when compared to WT mice; however, CEC only slightly modified the contraction induced by A61603. 7 The results indicate that the isolated mesenteric vascular bed of WT and KO α(1D)-AR mice expresses α(1A)-AR, that the pressor action of α(1A)-AR is up-regulated for α(1D)-AR in WT mice and suggest an important role of α(1B)-AR in the vascular pressure evoked by phenylephrine in KO α(1D)-AR mice.     

Noradrenergic modulation of serotonin release in rat dorsal and median raphé nuclei via alpha(1) and alpha(2A) adrenoceptors.

The rat rostral raphé nuclei receive catecholaminergic innervation from the locus coeruleus and other areas. In the present study, we investigated noradrenergic modulation of 5-HT release in rat dorsal and median raphé nuclei (DRN and MRN) slices (350 microm thick) superfused with artificial cerebrospinal fluid (aCSF). The raphé was locally stimulated (0.1 ms pulses, 10 mA) and 5-HT release was monitored at carbon fibre microelectrodes using fast cyclic voltammetry. The selective noradrenaline reuptake inhibitor desipramine (50 nM) did not increase stimulated (20 pulses, 100 Hz) 5-HT release but significantly slowed 5-HT reuptake in both DRN and MRN. On short stimulus trains (10 pulses, 200 Hz), the alpha(2)-selective agonist dexmedetomidine (10nM) decreased evoked 5-HT release in DRN and MRN (to 44+/-3 and 43+/-7% of pre-drug values, respectively, at minimum). In both nuclei, this response was antagonised by the selective alpha(2A)-antagonist BRL 44408 (1 microM: P<0.001 vs. dexmedetomidine) but not by the selective alpha(2B/C)-adrenoceptor antagonist ARC 239 (500 nM), the selective 5-HT(1A) antagonist WAY 100635 (100 nM) or the alpha(1)-selective antagonist prazosin (1 microM), suggesting that the effect of dexmedetomidine is wholly attributable to alpha(2A)-receptor activation. The alpha(1)-adrenoceptor agonist phenylephrine (5 microM) significantly decreased 5-HT release (to 49+/-7 and 41+/-4% of pre-drug values in DRN and MRN, respectively). The response was blocked by prazosin (P<0.001) and BRL 44408 (P<0.01) in DRN and by prazosin, BRL 44408 and WAY 100635 (all P<0.05) in MRN, suggesting that the effect of phenylephrine is, under these conditions, only partly mediated via alpha(1)-adrenoceptors. On long stimuli (30 pulses, 10 Hz), BRL 44408 (1 microM) increased evoked 5-HT efflux to 187+/-17 and 178+/-2% of pre-drug values in DRN and MRN, respectively (both P<0.001 vs. vehicle). Collectively, these data show that activation of both alpha(1) and alpha(2A)-adrenoceptors can decrease stimulated 5-HT release in the rostral raphé nuclei. Since the effect of dexmedetomidine was not antagonised by prazosin, we suggest that its effect was mediated directly, possibly through alpha(2A) receptors located on 5-HT cell elements, and not transduced indirectly through alpha(1)-adrenoceptor activation, as previously suggested by others.     

β-methasone-containing biodegradable poly(lactide-co-glycolide) acid microspheres for intraarticular injection: effect of formulation parameters on characteristics and in vitro release

A sustained drug release system based on the injectable poly(lactic-co-glycolic acid) (PLGA) microspheres loaded with β-methasone was prepared for localized treatment of rheumatic arthritis. The microscopy and structure of microspheres were characterized by scanning electron microscope (SEM) and Fourier transform infrared (FTIR). The effects of various formulation parameters on the properties of microspheres and in vitro release pattern of β-methasone were also investigated. The results demonstrated that increase in drug/polymer ratio led to increased particle size as well as drug release rate. Increase in PLGA concentration led to increased particle size, but decreased burst release. The drug encapsulation efficiency increased sharply by increasing polyvinyl alcohol (PVA) concentration in the aqueous phase from 1.5 to 2.0%. β-methasone release rate decreased considerately with decreasing OP (organic phase)/AP (aqueous phase) volume ratio. Stirring rate had significantly influence on the particle size and encapsulation efficiency. Independent of formulation parameters, β-methasone was slowly released from the PLGA microspheres over 11 days. The drug release profile of high drug loaded microspheres agree with Higuchi equation with a release mechanism of diffusion and erosion, that of middle drug loaded microspheres best agreed with Hixcon-Crowell equation and controlled by diffusion and erosion as well. The low drug loaded microspheres well fitted to logarithm normal distribution equation with mechanism of purely Fickian diffusion.     

Effects of Xanthoceraside on learning and memory impairment in mice induced by i.c.v.Aβ_(1-42)

Objective To investigate the improvement of Xanthoceraside on learning and memory impairment in mice induced by intracerebroventricular injection of Aβ1-42(i.c.v.Aβ1-42)and the possible mechanisms of its protection against AD.Methods Y-maze test,water-maze test and step-down test were used to investigate the learning and memory ability of mice;Biochemical analysis was used to detect the activity of CAT,T-AOC,ATPase and the content of MDA.Results The results showed that Xanthoceraside could significantly increase the alternation behavior in Y-maze test,shorten swimming time in water maze test and increase the latency and decrease the number of errors and the total time of shock in step-down test.Xanthoceraside markedly increased the activity of CAT,T-AOC,ATPase,at the same time,decreased the content of MDA.Conclusions Xanthoceraside can improve learning and memory impairment in mice induced by i.c.v.Aβ1-42 significantly.The mechanism may be associated with the protection against damage induced by free radicals;the inhibition of membrane lipid peroxidation and the improvement of metabolism of brain.     

The functional roles of poly(ethylene glycol)‐lipid and lysolipid in the drug retention and release from lysolipid‐containing thermosensitive liposomes in vitro and in vivo

Triggered release of liposomal contents following tumor accumulation and mild local heating is pursued as a means of improving the therapeutic index of chemotherapeutic drugs. Lysolipid‐containing thermosensitive liposomes (LTSLs) are composed of dipalmitoylphosphatidylcholine (DPPC), the lysolipid monostearoylphosphatidylcholine (MSPC), and poly(ethylene glycol)‐conjugated distearoylphosphatidylethanolamine (DSPE‐PEG₂₀₀₀). We investigated the roles of DSPE‐PEG₂₀₀₀ and lysolipid in the functional performance of the LTSL–doxorubicin formulation. Varying PEG‐lipid concentration (0–5 mol%) or bilayer orientation did not affect the release; however, lysolipid (0–10 mol%) had a concentration‐dependent effect on drug release at 42°C in vitro. Pharmacokinetics of various LTSL formulations were compared in mice with body temperature controlled at 37°C. As expected, incorporation of the PEG‐lipid increased doxorubicin plasma half‐life; however, PEG‐lipid orientation (bilayer vs. external leaflet) did not significantly improve circulation lifetime or drug retention in LTSL. Approximately 70% of lysolipid was lost within 1 h postinjection of LTSL, which could be due to interactions with the large membrane pool of the biological milieu. Considering that the present LTSL–doxorubicin formulation exhibits significant therapeutic activity when used in conjunction with mild heating, our current study provided critical insights into how the physicochemical properties of LTSL can be tailored to achieve better therapeutic activity. © 2009 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 2295–2308, 2010     

Multiple 5-HT(1) autoreceptor subtypes govern serotonin release in dorsal and median raphé nuclei

The present study investigated the possibility of multiple 5-HT(1) autoreceptor subtypes in the rostral raphé nuclei. Slices (350 microm) of rat dorsal or median raphé nucleus (DRN/MRN) were taken from male Wistar rats and superfused with artificial cerebrospinal fluid at 32 degrees C. Fast cyclic voltammetry at carbon fibre microelectrodes was used to monitor serotonin (5-HT) release following local electrical stimulation. In both DRN and MRN, 5-HT release on short trains was reduced by the selective 5-HT(1A) agonist 8-OH-DPAT (1 microM), an effect blocked by the selective 5-HT(1A) antagonist WAY 100635 (0.1 microM) but not by SB 216641 (0.05 and 0.2 microM) or BRL 15572 (0.5 microM), selective antagonists at the 5-HT(1B) and 5-HT(1D) receptors respectively. The selective 5-HT(1B) agonist CP 93129 (0.3 microM) also reduced 5-HT release in both nuclei. Its effect was blocked by SB 216641 but not by WAY 100635 or BRL 15572. The 5-HT(1D/1B) agonist sumatriptan (0.5 microM) decreased 5-HT release in both DRN and MRN. In DRN, the effect of sumatriptan was blocked by BRL 15572 but not by WAY 100635 or SB 216641. In MRN, the effect of sumatriptan was not blocked by any of the above antagonists. BRL 15572 increased 5-HT release on long stimulations in DRN and MRN while WAY 100635 had no effect. SB 216641 increased 5-HT release in MRN but not DRN. WAY 100635 potentiated the effect of SB 216641 in DRN but not MRN. The data suggest that 5-HT release in DRN is controlled by 5-HT(1A), 5-HT(1B) and 5-HT(1D) autoreceptors. 5-HT release in MRN is controlled by 5-HT(1A) and 5-HT(1B) autoreceptors and another, as yet unidentified mechanism.     

Species Variation in the Metabolism of R-(+)- and S-(-)-Nicotine by α-C- and N-Oxidation in vitro

Abstract

1. Marked species, but not sex differences, were observed in the metabolism of R-(+)- and S-(-)-nicotine to cotinine and the diastereoisomeric nicotine-1′-N-oxides by liver 10 000 × g supernatant preparations from rats, rabbits, mice, guinea-pigs and hamsters.

2. S-(-)-nicotine formed predominantly R,S-cis-nicotine-1′-N-oxide, whereas R-(+)-nicotine gave predominantly S,R-trans-nicotine-1′-N-oxide; stereoselective metabolism to cotinine also occurred. A stereo-selective site for the N-oxidation of nicotine is proposed to explain these results.     

Regulation of renal sympathetic neurotransmission by renal α(2A)-adrenoceptors is impaired in chronic renal failure

BACKGROUND AND PURPOSE

The mechanisms underlying increased renal noradrenaline in renal failure are still unclear. In this study, the role of α_2A-adrenoceptors in controlling sympathetic neurotransmission in chronic renal failure was evaluated in a subtotal nephrectomy model. Also, the influence of this receptor subtype on angiotensin II (Ang II)-mediated noradrenaline release was evaluated.

EXPERIMENTAL APPROACH

α_2A-Adrenoceptor-knockout (KO) and wild-type (WT) mice underwent subtotal (5/6) nephrectomy (SNx) or SHAM-operation (SHAM). Kidneys of WT and KO mice were isolated and perfused. Renal nerves were stimulated with platinum electrodes and noradrenaline release was measured by HPLC.

KEY RESULTS

Noradrenaline release induced by renal nerve stimulation (RNS) was significantly increased in WT mice after SNx. RNS-induced noradrenaline release was significantly higher in SHAM-KO compared with SHAM-WT, but no further increase in noradrenaline release could be observed in SNx-KO. α-Adrenoceptor antagonists increased RNS-induced noradrenaline release in SHAM-WT but not in SHAM-KO. After SNx, the effect of α₂-adrenoceptor blockade on renal noradrenaline release was attenuated in WT mice. The mRNA expression of α_2A-adrenoceptors was not altered, but the inhibitory effect of α₂-adrenoceptor agonists on cAMP formation was abolished after SNx. Ang II facilitated RNS-induced noradrenaline release in SHAM-WT but not in SHAM-KO and SNx-WT.

CONCLUSION AND IMPLICATIONS

In our model of renal failure autoregulation of renal sympathetic neurotransmission was impaired. Presynaptic inhibition of noradrenaline release was diminished and the facilitatory effect of presynaptic angiotensin AT₁ receptors on noradrenaline release was markedly decreased in renal failure and depended on functioning α_2A-adrenoceptors.     

In situ forming biodegradable poly(ε-caprolactone) microsphere systems: a challenge for transarterial embolization therapy. In vitro and preliminary ex vivo studies

Background: In situ forming biodegradable poly(ε-caprolactone) (PCL) microspheres (PCL-ISM) system was developed as a novel embolic agent for transarterial embolization (TAE) therapy of hepatocellular carcinoma (HCC). Ibuprofen sodium (Ibu-Na) was loaded on this platform to evaluate its potential for the treatment of post embolization syndrome.

Methods: The influence of formulation parameters on the size/shape, encapsulation efficiency and drug release was investigated using mixture experimental design. Regression models were derived and used to optimize the formulation for particle size, encapsulation efficiency and drug release profile for TAE therapy. An ex vivo model using isolated rat livers was established to assess the in situ formation of microspheres.

Results: All PCL-ISM components affected the studied properties and fitting indices of the regression models were high (Radj² = 0.810 for size, 0.964 encapsulation efficiency, and 0.993 or 0.971 for drug release at 30 min or 48 h). The optimized composition was: PCL = 4%, NMP = 43.1%, oil = 48.9%, surfactant = 2% and drug = 2%. Ex vivo studies revealed that PCL-ISM was able to form microspheres in the hepatic arterial bed.

Conclusions: PCL-ISM system provides a novel tool for the treatment of HCC and post-embolization syndrome. It is capable of forming microspheres with desirable size and Ibu-Na release profile after injection into blood vessels.     

In vivo growth-inhibition of Sarcoma 180 by an α-(1 → 4)-glucan–β-(1 → 6)-glucan-protein complex polysaccharide obtained from <Emphasis Type="Italic">Agaricus blazei</Emphasis> Murill

Agaricus blazei Murrill, a native mushroom of Brazil, has been widely consumed in different parts of the world due to its anticancer potential. This effect is generally attributed to its polysaccharides; however, the precise structure of these has not been fully characterized. To better understand the relationship between polysaccharide structures and antitumor activity, we investigated the effect of the intraperitoneally (i.p.) or orally (p.o.) administered α-(1 → 4)-glucan–β-(1 → 6)-glucan-protein complex polysaccharide from A. blazei alone or in association with 5-fluorouracil (5-FU) in tumor growth using Sarcoma 180 transplanted mice. Hematological, biochemical, and histopathological analyses were performed in order to evaluate the toxicological aspects of the polysaccharide treatment. The polysaccharide had no direct cytotoxic action on tumor cells in vitro. However, the polysaccharide showed strong in vivo antitumor effect. Thus, the tumor growth-inhibitory effect of the polysaccharide is apparently due to host-mediated mechanisms. The histopathological analysis suggests that the liver and the kidney were not affected by polysaccharide treatment. Neither enzymatic activity of transaminases (AST and ALT) nor urea levels were significantly altered. In hematological analysis, leucopeny was observed after 5-FU treatment, but this effect was prevented when the treatment was associated with the polysaccharide. In conclusion, this polysaccharide probably could explain the ethnopharmacological use of this mushroom in the treatment of cancer.     

Role of α1- and α2-GABA(A) receptors in mediating the respiratory changes associated with benzodiazepine sedation

BACKGROUND AND PURPOSE

The molecular substrates underlying the respiratory changes associated with benzodiazepine sedation are unknown. We examined the effects of different doses of diazepam and alprazolam on resting breathing in wild-type (WT) mice and clarified the contribution of α1- and α2-GABA_A receptors, which mediate the sedative and muscle relaxant action of diazepam, respectively, to these drug effects using point-mutated mice possessing either α1H101R- or α2H101R-GABA_A receptors insensitive to benzodiazepine.

EXPERIMENTAL APPROACH

Room air breathing was monitored using whole-body plethysmography. Different groups of WT mice were injected i.p. with diazepam (1–100 mg·kg⁻¹), alprazolam (0.3, 1 or 3 mg·kg⁻¹) or vehicle. α1H101R and α2H101R mice received 1 or 10 mg·kg⁻¹ diazepam or 0.3 or 3 mg·kg⁻¹ alprazolam. Respiratory frequency, tidal volume, time of expiration and time of inspiration before and 20 min after drug injection were analysed.

KEY RESULTS

Diazepam (10 mg·kg⁻¹) decreased the time of expiration, thereby increasing the resting respiratory frequency, in WT and α2H101R mice, but not in α1H101R mice. The time of inspiration was shortened in WT and α1H101R mice, but not in α2H101R mice. Alprazolam (1–3 mg·kg⁻¹) stimulated the respiratory frequency by shortening expiration and inspiration duration in WT mice. This tachypnoeic effect was partially conserved in α1H101R mice while absent in α2H101R mice.

CONCLUSIONS AND IMPLICATIONS

These results identify a specific role for α1-GABA_A receptors and α2-GABA_A receptors in mediating the shortening by benzodiazepines of the expiratory and inspiratory phase of resting breathing respectively.