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 IL1ß 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.

Cannabinoid CB2 Receptors Modulate Microglia Function and Amyloid Dynamics in a Mouse Model of Alzheimer's Disease.

The distribution and roles of the cannabinoid CB2 receptor in the CNS are still a matter of debate. Recent data suggest that, in addition to its presence in microglial cells, the CB2 receptor may be also expressed at low levels, yet biologically relevant, in other cell types such as neurons. It is accepted that the expression of CB2 receptors in the CNS is low under physiological conditions and is significantly elevated in chronic neuroinflammatory states associated with neurodegenerative diseases such as Alzheimer's disease. By using a novel mouse model (CB2 EGFP/f/f), we studied the distribution of cannabinoid CB2 receptors in the 5xFAD mouse model of Alzheimer's disease (by generating 5xFAD/CB2 EGFP/f/f mice) and explored the roles of CB2 receptors in microglial function. We used a novel selective and brain penetrant CB2 receptor agonist (RO6866945) as well as mice lacking the CB2 receptor (5xFAD/CB2 -/-) for these studies. We found that CB2 receptors are expressed in dystrophic neurite-associated microglia and that their modulation modifies the number and activity of microglial cells as well as the metabolism of the insoluble form of the amyloid peptide. These results support microglial CB2 receptors as potential targets for the development of amyloid-modulating therapies.

Deletion of H-Ras decreases renal fibrosis and myofibroblast activation following ureteral obstruction in mice.

Tubulointerstitial fibrosis is characterized by the presence of myofibroblasts that contribute to extracellular matrix accumulation. These cells may originate from resident fibroblasts, bone-marrow-derived cells, or renal epithelial cells converting to a mesenchymal phenotype. Ras GTPases are activated during renal fibrosis and play crucial roles in regulating both cell proliferation and TGF-beta-induced epithelial-mesenchymal transition. Here we set out to assess the contribution of Ras to experimental renal fibrosis using the well-established model of unilateral ureteral obstruction. Fifteen days after obstruction, both fibroblast proliferation and inducers of epithelial-mesenchymal transition were lower in obstructed kidneys of H-ras knockout mice and in fibroblast cell lines derived from these mice. Interestingly, fibronectin, collagen I accumulation, overall interstitial fibrosis, and the myofibroblast population were also lower in the knockout than in the wild-type mice. As expected, we found lower levels of activated Akt in the kidneys and cultured fibroblasts of the knockout. Whether Ras inhibition will turn out to prevent progression of renal fibrosis will require more direct studies.

Therapeutical relevance of MAP-kinase inhibitors in renal diseases: current knowledge and future clinical perspectives.

Renal failure, both acute and chronic, represents an important health problem by its social, sanitary and economic aspects. Mitogen-activated protein kinases (MAPK) are a family of mediators involved in the transduction of extracellular stimuli to intracellular responses. The best studied members of this family are extracellular signal-regulated kinases 1 and 2 (ERK1 and ERK2), Jun NH(2)-terminal kinase (JNK), p38 kinase and extracellular signal regulated kinases 5 (ERK5) also known as big MAP Kinase 1 (BMK1). MAPKs plays a role in regulating renal function and all these pathways have been demonstrated to be activated in many "in vivo" and cellular models or renal failure. As MAP kinases are key regulators in the control of cell proliferation and cell death, many more or less specific inhibitors of these pathways are being developed for the treatment of tumors. The purpose of this review is to examine the data available on the role of MAPKs activation in "in vivo" models of renal failure, as well as in different renal cell types (especially in mesangial cells, podocytes, tubular epithelial cells and fibroblasts) subjected to stress or damage. We have also reviewed the effect of MAPKs inhibition on renal damage, both "in vivo" and "in vitro". Data collected allow to suggest that therapy of chronic and acute renal disease with MAPKs inhibitors is a promising therapeutic area, although much more basic and clinical studies are necessary before this kind of therapy can be used in the everyday clinic.

Role of interleukin 1-beta in the inflammatory response in a fatty acid amide hydrolase-knockout mouse model of Alzheimer's disease.

The search for novel therapies for the treatment of Alzheimer's disease is an urgent need, due to the current paucity of available pharmacological tools and the recent failures obtained in clinical trials. Among other strategies, the modulation of amyloid-triggered neuroinflammation by the endocannabinoid system seems of relevance. Previous data indicate that the enhancement of the endocannabinoid tone through the inhibition of the enzymes responsible for the degradation of their main endogenous ligands may render beneficial effects. Based on previously reported data, in which we described a paradoxical effect of the genetic deletion of the fatty acid amide hydrolase, we here aimed to expand our knowledge on the role of the endocannabinoid system in the context of Alzheimer's disease. To that end, we inhibited the production of interleukin-1ß, one of the main inflammatory cytokines involved in the neuroinflammation triggered by amyloid peptides, in a transgenic mouse model of this disease by using minocycline, a drug known to impair the synthesis of this cytokine. Our data suggest that interleukin-1ß may be instrumental in order to achieve the beneficial effects derived of fatty acid amide hydrolase genetic inactivation. This could be appreciated at the molecular (cytokine expression, amyloid production, plaque deposition) as well as behavioral levels (memory impairment). We here describe a previously unknown link between the endocannabinoid system and interleukin-1ß in the context of Alzheimer's disease that open new possibilities for the development of novel therapeutics.

Endocannabinoid regulation of amyloid-induced neuroinflammation.

The modulation of endocannabinoid (EC) levels and the activation of cannabinoid receptors are seen as promising therapeutic strategies in a variety of diseases, including Alzheimer's disease (AD). We aimed to evaluate the effect of the pharmacologic and genetic inhibition of anandamide-degrading enzyme in a mouse model of AD (5xFAD). Pharmacologic inhibition of the fatty acid amide hydrolase (FAAH) had little impact on the expression of key enzymes and cytokines and also on the cognitive impairment, plaque deposition, and gliosis in 5xFAD mice. CB1 blockade exacerbated inflammation in this transgenic mouse model of AD. The genetic inactivation of FAAH led to increases in the expression of inflammatory cytokines. At the same time, FAAH-null 5xFAD mice exhibited a behavioral improvement in spatial memory that was independent of the level of anxiety and was not CB1 mediated. Finally, mice lacking FAAH showed diminished soluble amyloid levels, neuritic plaques, and gliosis. These data reinforce the notion of a role for the EC system in neuroinflammation and open new perspectives on the relevance of modulating EC levels in the inflamed brain.

Snail1-induced partial epithelial-to-mesenchymal transition drives renal fibrosis in mice and can be targeted to reverse established disease.

Progressive kidney fibrosis contributes greatly to end-stage renal failure, and no specific treatment is available to preserve organ function. During renal fibrosis, myofibroblasts accumulate in the interstitium of the kidney, leading to massive deposition of extracellular matrix and organ dysfunction. The origin of myofibroblasts is manifold, but the contribution of an epithelial-to-mesenchymal transition (EMT) undergone by renal epithelial cells during kidney fibrosis is still debated. We show that the reactivation of Snai1 (encoding snail family zinc finger 1, known as Snail1) in mouse renal epithelial cells is required for the development of fibrosis in the kidney. Damage-mediated Snail1 reactivation induces a partial EMT in tubular epithelial cells that, without directly contributing to the myofibroblast population, relays signals to the interstitium to promote myofibroblast differentiation and fibrogenesis and to sustain inflammation. We also show that Snail1-induced fibrosis can be reversed in vivo and that obstructive nephropathy can be therapeutically ameliorated in mice by targeting Snail1 expression. These results reconcile conflicting data on the role of the EMT in renal fibrosis and provide avenues for the design of novel anti-fibrotic therapies.