As populations increase their life expectancy, age-related neurodegenerative disorders such as Alzheimer's disease have become more common. I 2 -Imidazoline receptors (I 2 -IR) are widely distributed in the central nervous system, and dysregulation of I 2 -IR in patients with neurodegenerative diseases has been reported, suggesting their implication in cognitive impairment. This evidence indicates that high-affinity selective I 2 -IR ligands potentially contribute to the delay of neurodegeneration. In vivo studies in the female senescence accelerated mouse-prone 8 mice have shown that treatment with I 2 -IR ligands, MCR5 and MCR9, produce beneficial effects in behavior and cognition. Changes in molecular pathways implicated in oxidative stress, inflammation, synaptic plasticity, and apoptotic cell death were also studied. Furthermore, treatments with these I 2 -IR ligands diminished the amyloid precursor protein processing pathway and increased Aβ degrading enzymes in the hippocampus of SAMP8 mice. These results collectively demonstrate the neuroprotective role of these new I 2 -IR ligands in a mouse model of brain aging through specific pathways and suggest their potential as therapeutic agents in brain disorders and age-related neurodegenerative diseases.

The imidazoline I receptors (I-IRs) are widely distributed in the brain, and I-IR ligands may have therapeutic potential as neuroprotective agents. Since structural data for I-IR remains unknown, the discovery of selective I-IR ligands devoid of α-adrenoceptor (α-AR) affinity is likely to provide valuable tools in defining the pharmacological characterization of these receptors. We report the pharmacological characterization of a new family of (2-imidazolin-4-yl)phosphonates. Radioligand binding studies showed that they displayed a higher affinity for I-IRs than idazoxan, and high I/α selectivity. In vivo studies in mice showed that acute treatments with 1b and 2c significantly increased p-FADD/FADD ratio (an index of cell survival) in the hippocampus when compared with vehicle-treated controls. Additionally, acute and repeated treatments with 2c, but not with 1b, markedly reduced hippocampal p35 cleavage into neurotoxic p25. The present results indicate a neuroprotective potential of (2-imidazolin-4-yl)phosphonates acting at I-IRs.

Imidazoline I 2 receptors (I 2-IR), widely distributed in the CNS and altered in patients that suffered from neurodegenerative disorders, are orphan from the structural point of view and new I 2-IR ligands are urgently required for improving their pharmacological characterization. We report the synthesis and 3D-QSAR studies of a new family of bicyclic -iminophosphonates endowed with relevant affinities for human brain I 2-IR. Acute treatment in mice with a selected compound significantly decreased the FADD protein in the hippocampus, a key marker in neuroprotective actions. Additionally, in vivo studies in the familial Alzheimer's disease 5xFAD murine model revealed beneficial effects in behavior and cognition. These results are supported by changes in molecular pathways related to cognitive decline and Alzheimer's disease. Therefore bicyclic -iminophosphonates are tools that may open new therapeutic avenues for I 2-IR, particularly for unmet neurodegenerative conditions.

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Brain aging and dementia are current problems that must be solved. The levels of imidazoline 2 receptors (I2-IRs) are increased in the brain in Alzheimer's disease (AD) and other neurodegenerative diseases. We tested the action of the specific and selective I2-IR ligand B06 in a mouse model of accelerated aging and AD, the senescence-accelerated mouse prone 8 (SAMP8) model. Oral administration of B06 for four weeks improved SAMP8 mouse behavior and cognition and reduced AD hallmarks, oxidative stress, and apoptotic and neuroinflammation markers. Likewise, B06 regulated glial excitatory amino acid transporter 2 and N-methyl-D aspartate 2A and 2B receptor subunit protein levels.Calcineurin (CaN) is a phosphatase that controls the phosphorylation levels of cAMP response element-binding (CREB), apoptotic mediator BCL-2-associated agonist of cell death (BAD) and GSK3β, among other molecules. Interestingly, B06 was able to reduce the levels of the CaN active form (CaN A). Likewise, CREB phosphorylation, BAD gene expression, and other factors were modified after B06 treatment. Moreover, phosphorylation of a target of CaN, nuclear factor of activated T-cells, cytoplasmic 1 (NFATC1), was increased in B06-treated mice, impeding the transcription of genes related to neuroinflammation and neural plasticity. In summary, this I2 imidazoline ligand can exert its beneficial effects on age-related conditions by modulating CaN pathway action and affecting several molecular pathways, playing a neuroprotective role in SAMP8 mice. Table 1. Antibodies used in Western blot studies.