Potentiation of amyloid beta phagocytosis and amelioration of synaptic dysfunction upon FAAH deletion in a mouse model of Alzheimer's disease

BACKGROUND

The complex pathophysiology of Alzheimer's disease (AD) hampers the development of effective treatments. Attempts to prevent neurodegeneration in AD have failed so far, highlighting the need for further clarification of the underlying cellular and molecular mechanisms. Neuroinflammation seems to play a crucial role in disease progression, although its specific contribution to AD pathogenesis remains elusive. We have previously shown that the modulation of the endocannabinoid system (ECS) renders beneficial effects in a context of amyloidosis, which triggers neuroinflammation. In the 5xFAD model, the genetic inactivation of the enzyme that degrades anandamide (AEA), the fatty acid amide hydrolase (FAAH), was associated with a significant amelioration of the memory deficit.

METHODS

In this work, we use electrophysiology, flow cytometry and molecular analysis to evaluate the cellular and molecular mechanisms underlying the improvement associated to the increased endocannabinoid tone in the 5xFAD mouse- model.

RESULTS

We demonstrate that the chronic enhancement of the endocannabinoid tone rescues hippocampal synaptic plasticity in the 5xFAD mouse model. At the CA3-CA1 synapse, both basal synaptic transmission and long-term potentiation (LTP) of synaptic transmission are normalized upon FAAH genetic inactivation, in a CB1 receptor (CB1R)- and TRPV1 receptor-independent manner. Dendritic spine density in CA1 pyramidal neurons, which is notably decreased in 6-month-old 5xFAD animals, is also restored. Importantly, we reveal that the expression of microglial factors linked to phagocytic activity, such as TREM2 and CTSD, and other factors related to amyloid beta clearance and involved in neuron-glia crosstalk, such as complement component C3 and complement receptor C3AR, are specifically upregulated in 5xFAD/FAAH-/- animals.

CONCLUSION

In summary, our findings support the therapeutic potential of modulating, rather than suppressing, neuroinflammation in Alzheimer's disease. In our model, the long-term enhancement of the endocannabinoid tone triggered augmented microglial activation and amyloid beta phagocytosis, and a consequent reversal in the neuronal phenotype associated to the disease.

Cannabinoid CB2 receptors in the mouse brain: relevance for Alzheimer's disease

Background

Because of their low levels of expression and the inadequacy of current research tools, CB₂ cannabinoid receptors (CB₂R) have been difficult to study, particularly in the brain. This receptor is especially relevant in the context of neuroinflammation, so novel tools are needed to unveil its pathophysiological role(s).

Methods

We have generated a transgenic mouse model in which the expression of enhanced green fluorescent protein (EGFP) is under the control of the cnr2 gene promoter through the insertion of an Internal Ribosomal Entry Site followed by the EGFP coding region immediately 3′ of the cnr2 gene and crossed these mice with mice expressing five familial Alzheimer’s disease (AD) mutations (5xFAD).

Results

Expression of EGFP in control mice was below the level of detection in all regions of the central nervous system (CNS) that we examined. CB₂R-dependent-EGFP expression was detected in the CNS of 3-month-old AD mice in areas of intense inflammation and amyloid deposition; expression was coincident with the appearance of plaques in the cortex, hippocampus, brain stem, and thalamus. The expression of EGFP increased as a function of plaque formation and subsequent microgliosis and was restricted to microglial cells located in close proximity to neuritic plaques. AD mice with CB₂R deletion exhibited decreased neuritic plaques with no changes in IL1β expression.

Conclusions

Using a novel reporter mouse line, we found no evidence for CB₂R expression in the healthy CNS but clear up-regulation in the context of amyloid-triggered neuroinflammation. Data from CB₂R null mice indicate that they play a complex role in the response to plaque formation.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1174-9) contains supplementary material, which is available to authorized users.

Myeloid cell deficiency of p38γ/p38δ protects against candidiasis and regulates antifungal immunity

Candida albicans is a frequent aetiologic agent of sepsis associated with high mortality in immunocompromised patients. Developing new antifungal therapies is a medical need due to the low efficiency and resistance to current antifungal drugs. Here, we show that p38γ and p38δ regulate the innate immune response to C. albicans We describe a new TAK1-TPL2-MKK1-ERK1/2 pathway in macrophages, which is activated by Dectin-1 engagement and positively regulated by p38γ/p38δ. In mice, p38γ/p38δ deficiency protects against C. albicans infection by increasing ROS and iNOS production and thus the antifungal capacity of neutrophils and macrophages, and by decreasing the hyper-inflammation that leads to severe host damage. Leucocyte recruitment to infected kidneys and production of inflammatory mediators are decreased in p38γ/δ-null mice, reducing septic shock. p38γ/p38δ in myeloid cells are critical for this effect. Moreover, pharmacological inhibition of p38γ/p38δ in mice reduces fungal burden, revealing that these p38MAPKs may be therapeutic targets for treating C. albicans infection in humans.

Combined deletion of p38γ and p38δ reduces skin inflammation and protects from carcinogenesis

The contribution of chronic skin inflammation to the development of squamous cell carcinoma (SCC) is poorly understood. While the mitogen-activated protein kinase p38α regulates inflammatory responses and tumour development, little is known about the role of p38γ and p38δ in these processes. Here we show that combined p38γ and p38δ (p38γ/δ) deletion blocked skin tumour development in a chemically induced carcinogenesis model. p38γ/δ deletion reduced TPA-induced epidermal hyperproliferation and inflammation; it inhibited expression of proinflammatory cytokines and chemokines in keratinocytes in vitro and in whole skin in vivo, resulting in decreased neutrophil recruitment to skin. Our data indicate that p38γ/δ in keratinocytes promote carcinogenesis by enabling formation of a proinflammatory microenvironment that fosters epidermal hyperproliferation and tumourigenesis. These findings provide genetic evidence that p38γ and p38δ have essential roles in skin tumour development, and suggest that targeting inflammation through p38γ/δ offers a therapeutic strategy for SCC treatment and prevention.

Carpectomía proximal. Estudio por elementos finitos

Se realiza un análisis comparativo por elementos finitos del comportamiento de un modelo de muñeca sana con otro al que se le ha practicado una carpectomía proximal. Los parámetros valorados fueron las tensiones y áreas de contacto entre las superficies articulares del radio y semilunar en el modelo de la muñeca sana y entre el radio y la cabeza del hueso grande en el modelo de la muñeca con carpectomía proximal. Asimismo, se analizó el desplazamiento que experimenta el centroide de contacto en ambos modelos. De los resultados obtenidos se pudo comprobar que, a pesar de que se producen unas mayores tensiones, tanto en el radio como en la cabeza del hueso grande, éstas se distribuyen por un área mayor, es decir, cada zona articular del radio se encuentra menos tensionada por la cabeza del hueso grande y, por tanto, justificarían cómo una mayoría de pacientes a los que se les ha practicado una carpectomia proximal, no muestren un incremento en la tendencia a desarrollar una artrosis secundaria entre el radio y la cabeza del hueso grande. Por otra parte, el hecho de que durante el movimiento de flexoextensión se produce, no solo un movimiento de rotación sino también de traslación hacia el centro del radio, haría que se consiguiera una disipación adicional de tensiones.

Comparative performance of carbon isotope discrimination and canopy temperature depression as predictors of genotype differences in durum wheat yield in Spain

The relationships between carbon isotope discrimination (Δ) in mature kernels, canopy temperature depression (CTD) during anthesis and grain filling, 1000-kernel weight (TKW), total carbon content of mature kernels, and yield were studied in durum wheat (Triticum turgidum L. var. durum) grown in Spain (western Mediterranean basin). Twenty-five durum wheat genotypes were grown in 2 regions (NE and SE Spain) and under 2 water regimes (rainfed v. support irrigation) from 1997 to 1999 (i.e. a total of 12 trials). Principal component analysis placed yield and Δ on the same axis. Pearson’s correlation and stepwise analysis confirmed that Δ was the trait that best assessed genotype differences in yield within trials, and was followed, at a considerable distance, by TKW. Our results also demonstrated the extremely poor performance of CTD throughout the wide range of growing conditions in this study.

Photosynthetic and developmental traits associated with genotypic differences in durum wheat yield across the Mediterranean basin

The relationships between various morphophysiological traits and yield were studied in durum wheat (Triticum durum Desf.) grown in Mediterranean conditions. Two sets of 22 genotypes were used. One was developed for semi-humid environments (TA-genotypes) and was cultivated in 22 trials around the Mediterranean basin with a mean yield across genotypes and environments of 4925 kg/ha. The other set was developed for drier conditions (CA-genotypes) and was cultivated in 15 trials, with a mean yield of 3501 kg/ha. Morphophysiological traits for each set were evaluated in 2 trials with contrasting water regimes conducted in north-eastern Spain: Lleida-rainfed (LR) and Lleida-irrigation (LI). Two kinds of traits were evaluated: developmental traits, including early vigour, plant height, and phenology (days from planting to heading and to maturity); and traits related to photosynthetic performance such as canopy temperature and chlorophyll content of the flag leaf, both measured during grain filling, and carbon isotope discrimination of mature grains. All the traits, measured in both Lleida trials, were related to the mean yield of the same genotypes across all the sites where they were cultivated. Yield measured at either of the 2 environments at Lleida was a much poorer predictor of genotype differences in mean yield than most of the traits. Nevertheless, the kind of environment where the morphophysiological traits were evaluated affected the performance of these traits as yield predictors. The combination of significant traits measured in the better environment (LI) explained 71% and 55% of genotype variability in yield within TA- and CA-genotypes, respectively, but only 56% and 27% when they were evaluated at LR. On the other hand, growing conditions of the yield trials was the main factor determining the best combination of traits. For TA-genotypes, larger yields were associated with shorter plants and higher carbon isotope discrimination (Δ) of grains, and to a lesser extent with higher early vigour and lower canopy temperature, whereas phenological traits made no contribution to explaining genotype differences in yield. For the CA-genotypes, higher yields were related to an earlier heading date or alternatively to a higher chlorophyll content during grain filling. A higher Δ in mature kernels also seems to be a positive trait.

Bromocriptine in the management of infertile men after surgery of prolactin secreting adenomas

This study evaluated bromocriptine treatment in nine patients with prolactin secreting adenomas who continued to have elevated circulating levels of prolactin after surgery, and who were interested in improving their sperm counts. These patients were brought into the study 3.2 +/- 1.8 years (mean +/- SD) after surgery. All of them presented with high circulating levels of prolactin, and eight of the patients had oligozoospermia (range 0-10 X 10(6) spermatozoa/ml). LH and testosterone levels were low in seven patients, and eight patients had low FSH values. All patients were treated for 90 days with 7.5 mg/day of bromocriptine. After treatment, prolactin levels decreased significantly in all patients, while sperm counts increased significantly in five of them. Testosterone levels increased in four subjects. Bromocriptine therefore seems useful in the management of this type of patient because of the observed decline in prolactin levels and the increase in sperm counts. Possible mechanisms involved in this action are discussed.

D-tryptophan-6-LH-RH-at los doses in the treatment of male subfertility

The aim of this trial was to evaluate the effect of D-TRP-6-LH-RH in patients with idiopathic normogonadotropic oligoasthenozoospermia (I.N.O.). The LH and FSH response to LH-RH before and during treatment was also studied. Seven patients (age 27 to 32 years) with long standing infertility were incorporated. All of them were considered to have I.N.O. on the basis of at least three spermatograms and absence of evidence of other diseases. All patients were treated wtih D-TRP-6-LH-RH (2 microgram i.m. every two days) during 90 days. Control spermatograms were performed at monthly intervals during and after treatment. The responses of LH and FSH to 50 microgram i.v. LH-RH were studied before and after 90 days of treatment. Five of the patients achieved a normalization of the concentration of spermatozoa per ml and of the percentage of forwardly progressive spermatozoa. None of the patients showed inhibition of the response to LH and FSH to LH-RH during treatment. These results differ from others in which larger doses of D-TRP-6-LH-RH determined an inhibition of the pituitary response to LH-RH and an impairment of the spermogram.

Plasma levels of norepinephrine during the periovulatory period in normal women. Further studies

Eleven normally cycling women in whom laparotomy was indicated for benign gynecologic pathology were studied. Surgery was performed on day 0 (expected day of ovulation). Blood samples were drawn daily from day -8 to day -4, and every 8 hours from day -3 to day +2; estradiol (E2), progesterone (P), norepinephrine (NE), and LH were determined by RIA. Ovulation was certified by ovarian visualization and biopsy during laparotomy. In nine ovulatory patients mean E2 peak was found 48 hours before LH peak. Mean NE levels showed minimal variations until 48 hours before LH peak; 8 hours after E2 peak mean NE values increased significantly, fell 8 hours later, and rose immediately again, reaching maximal levels 24 hours after E2 peak. These values remained high until 16 hours before the LH peak and decreased gradually, thereafter reaching basal levels 32 hours after LH peak. Two anovulatory patients showed an atypical pattern of ovarian steroids and LH secretion and NE showed large variations without any correlation with estradiol or LH levels. This study confirms previous findings in women and experimental work in animals regarding the existence of a noradrenergic trigger mechanism to the LH ovulatory discharge.

Studies on the mode of action of somatostatin on insulin secretion

The effect of somatostatin on insulin release by incubated slices of rat pancreas was studied. Somatostatin inhibited insulin release induced by arginine/glucose (A/G), glucagon, glibenclamide, pentoxifyllin, 3',5'-adenosine monophosphate (cAMP), phentolamine, and KCl. When A/G was used as a stimulus, the quantial inhibitory effect of somatostatin was not neutralized by progressively increasing glucose concentrations. The alpha adrenergic blocking agent phentolamine, the phosphodiesterase inhibitors theophylline (10 mM) or pentoxifyllin (10 mM), and KCl partially reversed the inhibitory effect of somatostatin on A/G stimulation. The maximal reversal of somatostatin inhibition was obtained when the slices of pancreas were stimulated with A/G in the presence of the calcium ioniphore A23187 plus ATP. These results suggest that the inhibitory effect of somatostatin on insulin secretion could result from calcium translocation in pancreatic beta cells.

The influence of pentoxyfylline [1-(5-oxohexyl-) 3,7-dimethylxanthine] (BL 191) on the insulin secretion induced by glibenclamide and by arginine/glucose in the perfused pancreas

Pharmacodynamic characteristics of pentoxyfylline (BL 191) related to insulin secretion by the isolated perfused rat pancreas are studied. The results obtained show that: 1) BL 191 (5 mM) is capable of stimulating insulin secretion, even in the presence of another stimulator; 2) BL 191 increases both phases of the secretion produced by constant arginine 20 mM/glucose 5 mM perfusion; 3) BL 191 significantly increases and turns biphasic the monophasic insulin secretion pattern produced by 1 microgram/ml glibenclamide; 4) the effects mentioned in points 2) and 3) are inhibited if the phosphodiesterase activator imidazole (300 mg/100 ml) is present in the perfusion medium; 5) the phosphodiesterase inhibitor theophylline has the same effects as BL 191, except for its inability to stimulate insulin release in the absence of another stimulator; 6) somatostatin (100 ng/ml) significantly inhibits insulin secretion produced by arginine/glucose or glibenclamide, as well as by arginine, glucose plus theophylline or BL 191, and by glibenclamide plus theophylline or BL 191, in both cases the inhibitory effect of somatostatin is reduced by the presence of BL 191 or theophylline.

Effect of a new benzodiazepine derivate, clobazam, in anxious patients with gastrointestinal disorders

Thirty-four anxious patients with gastrointestinal disorders were studied in order to evaluate the effectiveness of a new 1,5-benzodiazepine antianxiety agent (HR 376). The disorders were classified as organic or functional according to the presence or absence of radiologic signs of ulcer. Dietetic measures, gastric antacids, anticholinergic agents, and antianxiety treatment were applied for six weeks. Anxiolytic treatment consisted of 30 mg/day clobazam (HR 376) or 15 mg/day diazepam, given in a randomized, double-blind manner. Clinical follow-up was performed with the PEN Personality Inventory (PEN), Taylor Manifest Anxiety Scale (TMAS), Hamilton Anxiety Scale (HAS), and Wittenborn Psychiatric Rating Scales (WPRS). The score of the psychoticism dimension of the PEN inventory was significantly higher in organic than in functional patients. Significant differences occurred in the reduction of the rating scores of HAS and WPRS before/after treatment in the clobazam and diazepam groups. This would express a modification of state anxiety. The TMAS, which evaluates trait anxiety, disclosed statistically significant improvement in the clobazam group. This group showed an early reduction of the HAS and TMAS scores, which would suggest an early onset of action.

Luteinizing hormone-releasing hormone in the treatment of anovultory infertility

Fifteen infertile, anovulatory women, ages 20 to 37, were treated with synthetic luteinizing hormone-releasing hormone (LH-RH) to stimulate follicular maturation and/or ovulation. Thirteen of the patients had been treated unsuccessfully with other therapeutic regimens. To obtain follicular maturation, LH-RH was given intramuscularly in daily doses of 25 mu-g for 7 days and 50 mu-g for the next 7 days, or 100 mu-g for 3 days and 150 mu-g for the next 3 days. Both regimens were begun on the 4th day of a spontaneous or induced cycle. Follicular maturation (evaluated by the cervical mucus scale) occurred in three of seven cycles treated withe the first regimen and three of five treated with the second regimen. To induce ovulation, LH-RH was given in intravenous infusion (50 to 500 mu-g), intramuscularly (100 mu-g), or in a combination of both methods. The drug was administered after follicular maturation with LH-RH, clomiphene citrate, or human menopausal gonadotropin had been achieved; it was also given during four cycles in which spontaneous follicular maturation had occurred. Ovulation occurred in 10 of 25 treated cycles. Five pregnancies resulted, three in the first post-treatment cycle.