Regulation of inflammation by cannabinoids, the endocannabinoids 2-arachidonoyl-glycerol and arachidonoyl-ethanolamide, and their metabolites

2-Arachidonoyl-glycerol (2-AG) and arachidonyl-ethanolamide (AEA) are endocannabinoids that have been implicated in many physiologic disorders, including obesity, metabolic syndromes, hepatic diseases, pain, neurologic disorders, and inflammation. Their immunomodulatory effects are numerous and are not always mediated by cannabinoid receptors, reflecting the presence of an arachidonic acid (AA) molecule in their structure, the latter being the precursor of numerous bioactive lipids that are pro- or anti-inflammatory. 2-AG and AEA can thus serve as a source of AA but can also be metabolized by most eicosanoid biosynthetic enzymes, yielding additional lipids. In this regard, enhancing endocannabinoid levels by using endocannabinoid hydrolysis inhibitors is likely to augment the levels of these lipids that could regulate inflammatory cell functions. This review summarizes the metabolic pathways involved in the biosynthesis and metabolism of AEA and 2-AG, as well as the biologic effects of the 2-AG and AEA lipidomes in the regulation of inflammation.

2-Arachidonoyl-glycerol- and arachidonic acid-stimulated neutrophils release antimicrobial effectors against E. coli, S. aureus, HSV-1, and RSV

The endocannabinoid 2-AG is highly susceptible to its hydrolysis into AA, which activates neutrophils through de novo LTB(4) biosynthesis, independently of CB activation. In this study, we show that 2-AG and AA stimulate neutrophils to release antimicrobial effectors. Supernatants of neutrophils activated with nanomolar concentrations of 2-AG and AA indeed inhibited the infectivity of HSV-1 and RSV. Additionally, the supernatants of 2-AG- and AA-stimulated neutrophils strongly impaired the growth of Escherichia coli and Staphylococcus aureus. This correlated with the release of a large amount (micrograms) of α-defensins, as well as a limited amount (nanograms) of LL-37. All the effects of AA and 2-AG mentioned above were prevented by inhibiting LTB(4) biosynthesis or by blocking BLT(1). Importantly, neither CB(2) receptor agonists nor antagonists could mimic nor prevent the effects of 2-AG, respectively. In fact, qPCR data show that contaminating eosinophils express ∼100-fold more CB(2) receptor mRNA than purified neutrophils, suggesting that CB(2) receptor expression by human neutrophils is limited and that contaminating eosinophils are likely responsible for the previously documented CB(2) expression by freshly isolated human neutrophils. The rapid conversion of 2-AG to AA and their subsequent metabolism into LTB(4) promote 2-AG and AA as multifunctional activators of neutrophils, mainly exerting their effects by activating the BLT(1). Considering that nanomolar concentrations of AA or 2-AG were sufficient to impair viral infectivity, this suggests potential physiological roles for 2-AG and AA as regulators of host defense in vivo.

Leukotriene D4 and interleukin-13 cooperate to increase the release of eotaxin-3 by airway epithelial cells

INTRODUCTION

Airway epithelial cells play a central role in the physiopathology of asthma. They release eotaxins when treated with T(H)2 cytokines such as interleukin (IL)-4 or IL-13, and these chemokines attract eosinophils and potentiate the biosynthesis of cysteinyl leukotrienes (cysLTs), which in turn induce bronchoconstriction and mucus secretion. These effects of cysLTs mainly mediated by CysLT(1) and CysLT(2) receptors on epithelial cell functions remain largely undefined. Because the release of inflammatory cytokines, eotaxins, and cysLTs occur relatively at the same time and location in the lung tissue, we hypothesized that they regulate inflammation cooperatively rather than redundantly. We therefore investigated whether cysLTs and the T(H)2 cytokines would act in concert to augment the release of eotaxins by airway epithelial cells.

METHODS

A549 cells or human primary bronchial epithelial cells were incubated with or without IL-4, IL-13, and/or LTD(4). The release of eotaxin-3 and the expression of cysLT receptors were assessed by ELISA, RT-PCR, and flow cytometry, respectively.

RESULTS

IL-4 and IL-13 induced the release of eotaxin-3 by airway epithelial cells. LTD(4) weakly induced the release of eotaxin-3 but clearly potentiated the IL-13-induced eotaxin-3 release. LTD(4) had no effect on IL-4-stimulated cells. Epithelial cells expressed CysLT(1) but not CysLT(2). CysLT(1) expression was increased by IL-13 but not by IL-4 and/or LTD(4). Importantly, the upregulation of CysLT(1) by IL-13 preceded eotaxin-3 release.

CONCLUSIONS

These results demonstrate a stepwise cooperation between IL-13 and LTD(4). IL-13 upregulates CysLT(1) expression and consequently the response to cysLTs This results in an increased release of eotaxin-3 by epithelial cells which at its turn increases the recruitment of leukocytes and their biosynthesis of cysLTs. This positive amplification loop involving epithelial cells and leukocytes could be implicated in the recruitment of eosinophils observed in asthmatics.

Hypothermia and Alzheimer's disease neuropathogenic pathways

Alzheimer's disease (AD) remains a major health problem, and accounts for 50 to 60% of all cases of dementia. The two histopathological hallmarks of AD are senile plaques, composed of the β-amyloid peptide (Aβ), and intraneuronal neurofibrillary tangles composed of abnormally hyperphosphorylated tau protein. Only a small proportion of AD is due to mutations in the genome of patients, the large majority of cases being of late onset and sporadic in origin. The relative contribution of genetics and environment to the sporadic cases is unclear, but they are accepted to be of multifactorial origin. This means that genetic and environmental factors can interact together to induce or accelerate the disease. Among environmental factors, studies suggest that hypothermia may contribute to the development and exacerbation AD. Here, we review the preclinical data involving hypothermia with tau and Aβ, as well as clinical evidence implicating hypothermia in the development of AD.

The endocannabinoid 2-arachidonoyl-glycerol activates human neutrophils: critical role of its hydrolysis and de novo leukotriene B4 biosynthesis

Although endocannabinoids are important players in nociception and obesity, their roles as immunomodulators remain elusive. The main endocannabinoids described to date, namely 2-arachidonoyl-glycerol (2-AG) and arachidonyl-ethanolamide (AEA), induce an intriguing profile of pro- and anti-inflammatory effects. This could relate to cell-specific cannabinoid receptor expression and/or the action of endocannabinoid-derived metabolites. Importantly, 2-AG and AEA comprise a molecule of arachidonic acid (AA) in their structure and are hydrolyzed rapidly. We postulated the following: 1) the released AA from endocannabinoid hydrolysis would be metabolized into eicosanoids; and 2) these eicosanoids would mediate some of the effects of endocannabinoids. To confirm these hypotheses, experiments were performed in which freshly isolated human neutrophils were treated with endocannabinoids. Unlike AEA, 2-AG stimulated myeloperoxidase release, kinase activation, and calcium mobilization by neutrophils. Although 2-AG did not induce the migration of neutrophils, it induced the release of a migrating activity for neutrophils. 2-AG also rapidly (1 min) induced a robust biosynthesis of leukotrienes, similar to that observed with AA. The effects of 2-AG were not mimicked nor prevented by cannabinoid receptor agonists or antagonists, respectively. Finally, the blockade of either 2-AG hydrolysis, leukotriene (LT) B(4) biosynthesis, or LTB(4) receptor 1 activation prevented all the effects of 2-AG on neutrophil functions. In conclusion, we demonstrated that 2-AG potently activates human neutrophils. This is the consequence of 2-AG hydrolysis, de novo LTB(4) biosynthesis, and an autocrine activation loop involving LTB(4) receptor 1.

Enzymatic degradation of cross-linked high amylose starch tablets and its effect on in vitro release of sodium diclofenac

The influence of several physicochemical parameters on enzymatic hydrolysis and the in vitro release of sodium diclofenac (SDic) from cross-linked high amylose starch (Contramid) (CLA) tablets was evaluated. These parameters included pH, ionic strength of the medium, enzyme concentration, compression force and incorporation of gel-forming polymers such as hydroxypropyl methylcellulose (HPMC), poly(ethylene oxide) (PEO) and poly(vinyl alcohol) into the tablet. Pure CLA tablets were incubated in phosphate buffer (pH 6.8) containing alpha-amylase and the extent of enzymatic erosion was determined by gravimetry. Release of SDic from CLA tablets, in the presence of alpha-amylase, was measured using a USP type III dissolution apparatus. For low alpha-amylase concentrations (<2250 IU/l), the drug release was mainly diffusion-controlled. At higher alpha-amylase concentrations (>4500 IU/l) both diffusion and erosion contributed to the release of SDic. The hydrolysis kinetics of CLA tablets by alpha-amylase was biphasic. During the first phase (2-4 h), the hydrolysis rate was hyperbolically related to the alpha-amylase concentration but was practically alpha-amylase concentration-independent during the second phase. Enzymatic erosion and drug release kinetics appear to be relatively independent of ionic strength, pre-incubation time in simulated gastric fluid, and compression force of the tablets (6-34 kN). Incorporation of HPMC or PEO into the tablet resulted in a significant decrease of both tablet erosion and drug release rates.

Characterization of cytohesin-1 monoclonal antibodies: expression in neutrophils and during granulocytic maturation of HL-60 cells

ADP-ribosylation factors (Arf) are small GTP-binding proteins involved in vesicular transport and the activation of phospholipase D (PLD). The conversion of Arf-GDP to Arf-GTP is promoted in vivo by guanine nucleotide exchange factors such as ARNO or cytohesin-1. In order to examine the expression of ARNO and cytohesin-1 in human granulocytes, we generated specific polyclonal and monoclonal antibodies (mAbs). We also overexpressed GFP-ARNO and GFP-cytohesin-1 in RBL-2H3 cells to characterize the specificity and the ability of cytohesin-1 mAbs to immunoprecipitate cytohesin-1. Among the hybridomas secreting cytohesin-1 mAbs, only the clones 2E11, 1E4, 3C8, 6F5, 4C7, 7A3 and 8F7 were found to be specific for cytohesin-1. Furthermore, mAb 2E11 immunoprecipitated GFP-cytohesin-1 but not GFP-ARNO under native conditions. In contrast, mAbs 5D8, 4C3, 2G8, 6G11, 4C3, 6D4, 7B4 and 6F8 detected both cytohesin-1 and ARNO as monitored by immunoblotting. Although mAb 6G11 detected both proteins, this antibody immunoprecipitated GFP-ARNO but not GFP-cytohesin-1 under native conditions. Another antibody, mAb 10A12, also selectively immunoprecipitated GFP-ARNO under native conditions, but the epitope recognized by this mAb is unlikely to be linear as no signal was obtained by immunoblotting. Immunoprecipitation with a cytohesin-1 polyclonal antibody and blotting with cytohesin-1 specific mAbs revealed that cytohesin-1 is highly expressed in neutrophils. Cytohesin-1 can be detected in HL-60 cells but the endogenous protein levels were low in undifferentiated cells. Using the specific cytohesin-1 mAb 2E11 we observed a marked increase in levels of cytohesin-1 expression during dibutyryl-cyclic AMP-induced granulocytic differentiation of HL-60 cells. These data suggest that cytohesin-1, which may have important functions in neutrophil physiology, can be useful as a potential marker for granulocytic differentiation.

Cross-linked high amylose starch for controlled release of drugs: recent advances

Cross-linked high amylose starches have been developed as excipients for the formulation of controlled-release solid dosage forms for the oral delivery of drugs. Advantages of this new class of excipients include cost-effectiveness, readily accessible industrial manufacturing technology, high active ingredient core loading and the possibility of achieving a quasi zero-order release for most drugs. In addition to the latter, other features distinguish cross-linked high amylose starches from other excipients used to prepare hydrophilic matrices. Among these are the absence of erosion, the limited swelling and the fact that increasing cross-linking degrees results in increased water uptake rate, drug release rate and equilibrium swelling. Thus the goal of the present study was to gain some insights into the mechanism of drug release control by matrices of cross-linked high amylose starch. Water transport kinetics and dimensional changes were studied in matrices placed in water at 37 degrees C by an image analysis technique. The results show that in the first 5 min, a gel layer is formed at the surface of the tablet, after which the gel front seems to halt its progression toward the center of the tablet. Water continues to diffuse through the front and to invade the core. As a consequence, this latter swells, with a predominance for radial swelling. Equilibrium swelling is reached over 3 days, when the water concentration in the tablet becomes homogeneous and the whole tablet gelifies. Solid-state 13C-NMR were acquired on cross-linked high amylose starch powders, tablets and hydrated tablets with varying cross-linking degrees. They show a predominance of the V-type single helix arrangement of amylose in the dry state irrespective of the cross-linking degree. Upon hydration, the homologues with a low cross-linking degrees show a transition from the V to the B-type double helix arrangement. It is therefore hypothesized that the capacity of amylose to undergo the V to B transition is an important factor in controlling water transport and drug release rate. Finally applications to different drugs are reviewed briefly. They illustrate the versatility of this technology as generic versions of zero order OROS drug (Efidac) and Fickian release conventional matrices (Voltaren SR) were developed and successfully tested in pilot clinical studies to be bioequivalent to the references. These studies further showed that cross-linked high amylose starch matrices have the lowest inter-subject variability among the systems tested and show a total absence of food effect.

Poly(alkylcyanoacrylate) nanocapsules: physicochemical characterization and mechanism of formation

Nanocapsules of poly(isobutylcyanoacrylate) and poly(isohexylcyanoacrylate) were prepared by addition of the monomer to an organic phase and subsequent mixing of the organic phase to an aqueous phase containing poloxamer 188, 238 or 407. Gel permeation chromatography indicated that in contrast to literature reports, polymerization occurred in the organic phase and nanocapsules were obtained by interfacial precipitation of the polymer without any significant change of the molecular weight. Addition of SO2 to the organic phase before the introduction of the monomer allowed preparation of nanocapsules with a lower molecular weight. Nanospheres were prepared in a similar way albeit using an organic phase that was completely miscible within the aqueous phase so that solid spheres were obtained. Density gradient centrifugation revealed that nanocapsules had a density intermediate between nanospheres and an emulsion prepared in the same way without addition of monomer to the organic phase. Further, the process used to prepare nanocapsules had a high yield since no oil droplets or nanospheres were obtained by this process. Zeta potential of the nanocapsules and spheres was found to be related to the molecular weight of the polymer: values as high as approximately -42 mV were obtained for low molecular weight nanocapsules (MW approximately 1000) compared to approximately -10mV for the emulsion and the high molecular weight nanocapsules (MW approximately 100,000). Surface charge of the nanocapsules and molecular weight of their polymeric wall conditioned the adsorption capacity of poloxamers. Moreover, the highest adsorption was measured with the most hydrophobic poloxamer. These observations agree with previous work conducted on hydrophobic surfaces.

Association of cyclosporin to isohexylcyanoacrylate nanospheres and subsequent release in human plasma in vitro

Polyisohexylcyanoacrylate nanocapsules containing cyclosporin were prepared by mixing in a 1:2 ratio an oil/ethanol solution of monomer and drug with an aqueous phase. Drug nanoencapsulation rate was controlled by its partition coefficient between the inner (organic) and outer (aqueous) phases. Thus highest encapsulation yields (88 per cent) were achieved by reducing cyclosporin solubility in the aqueous phase, i.e. by reducing ethanol concentration under reduced pressure, achieving a 3-fold volume reduction. Due to the relative insolubility of cyclosporin in water, no drug was released from the nanocapsules during storage in this injectable vehicle. Upon a 1/5 dilution in human plasma at 37 degrees C in vitro around 40 per cent of the initially encapsulated cyclosporin diffused quickly out of the capsules and an equilibrium was reached, the drug being most likely dissolved in the fatty compartment of the plasma such as lipoproteins, etc. This release mechanism is different from plain polymeric nanoparticles. Indeed, in this case the drug was released in two phases: an initial burst (around 60 per cent) of adsorbed drug as a result of the dilution, followed by a slow release (around 20 per cent over 3 h) which is likely to result from the progressive enzymatic erosion of the polymer. The initial burst was markedly more pronounced (around 80 per cent) when nanoparticle suspensions were evaporated to 1/3 of their initial volume under reduced pressure. Finally, experiments performed at 0 degree C allowed a reduction of the fraction released immediately from both types of nanospheres, probably because of a reduced solubility in plasma. In the case of nanoparticles the second phase of slow release is also inhibited at 0 degree C, in agreement with an enzymatically controlled release mechanism.

Biodegradable nanospheres containing phthalocyanines and naphthalocyanines for targeted photodynamic tumor therapy

Preparation methods of cyanoacrylic nanocapsules or nanoparticles containing phthalocyanines and naphthalocyanines are described. Nanocapsules were obtained by interfacial polymerization in an oil-in-water emulsion. Drug encapsulation efficiency depended upon drug concentration, ethanol concentration, and phthalocyanine sulfonation degree and reached 100% in some cases. Nanocapsules size ranged from 150 to 250 nm and varied with phthalocyanine sulfonation degree and pH of the aqueous phase. Nanoparticles were prepared by the addition of monomer to an aqueous phase containing hydrophilic phthalocyanine derivatives. Depending upon the pH, sizes ranged from 10 to 380 nm. Drug binding was between 75 and 80%. These new preparations could prove useful in the photodynamic treatment of tumors.