Pharmacological Strategies for Cataract Management: From Molecular Targets to Clinical Translation.

Cataracts, characterized by the opacification of the eye lens, remain a leading cause of reversible blindness globally. Age and diabetes are key risk factors, and with the increasing aging and diabetic population, the global burden of cataracts is projected to rise significantly. Current treatment is predominantly surgical; however, pharmacological strategies could offer a non-invasive alternative with the potential to delay, prevent, or even reverse cataract progression.

The Role of the Ubiquitin System in Eye Diseases.

The ubiquitin-proteasome system (UPS) is a fundamental process that regulates various biological functions, including immune response, cell cycle, oxidative stress, migration, and cellular proliferation. This system is responsible for the degradation of proteins, while proteasomes play a significant role in mechanisms involved in health and human diseases. The participation of the UPS in immune response is particularly relevant, leading to the involvement of immunoproteasomes.

P2X7R antagonism suppresses long-lasting brain hyperexcitability following traumatic brain injury in mice.

Post-traumatic epilepsy (PTE) is one of the most common life-quality reducing consequences of traumatic brain injury (TBI). However, to date there are no pharmacological approaches to predict or to prevent the development of PTE. The P2X7 receptor (P2X7R) is a cationic ATP-dependent membrane channel that is expressed throughout the brain.

Opposing effects of the purinergic P2X7 receptor on seizures in neurons and microglia in male mice.

Background: The purinergic ATP-gated P2X7 receptor (P2X7R) is increasingly recognized to contribute to pathological neuroinflammation and brain hyperexcitability. P2X7R expression has been shown to be increased in the brain, including both microglia and neurons, in experimental models of epilepsy and patients. To date, the cell type-specific downstream effects of P2X7Rs during seizures remain, however, incompletely understood.

CPEB4-CLOCK crosstalk during temporal lobe epilepsy.

Objective: Posttranscriptional mechanisms are increasingly recognized as important contributors to the formation of hyperexcitable networks in epilepsy. Messenger RNA (mRNA) polyadenylation is a key regulatory mechanism governing protein expression by enhancing mRNA stability and translation. Previous studies have shown large-scale changes in mRNA polyadenylation in the hippocampus of mice during epilepsy development.

Functional expression of the ATP-gated P2X7 receptor in human iPSC-derived astrocytes.

Activation of the ATP-gated P2X7 receptor (P2X7R), implicated in numerous diseases of the brain, can trigger diverse responses such as the release of pro-inflammatory cytokines, modulation of neurotransmission, cell proliferation or cell death. However, despite the known species-specific differences in its pharmacological properties, to date, most functional studies on P2X7R responses have been analyzed in cells from rodents or immortalised cell lines. To assess the endogenous and functional expression of P2X7Rs in human astrocytes, we differentiated human-induced pluripotent stem cells (hiPSCs) into GFAP and S100 β-expressing astrocytes.

Analyzing the Role of the P2X7 Receptor in Epilepsy.

Purinergic signaling is increasingly recognized to play a role during the generation of hyperexcitable networks in the brain. Among the purinergic receptors, the ionotropic ATP-gated P2X7 receptor has attracted particular attention as a possible drug target for epilepsy. P2X7 receptor expression is increased in the brain of experimental models of epilepsy and in patients and, P2X7 receptor antagonism modulates seizure severity and epilepsy development.

Increased expression of the ATP-gated P2X7 receptor reduces responsiveness to anti-convulsants during status epilepticus in mice.

Background And Purpose: Refractory status epilepticus is a clinical emergency associated with high mortality and morbidity. Increasing evidence suggests neuroinflammation contributes to the development of drug-refractoriness during status epilepticus. Here, we have determined the contribution of the ATP-gated P2X7 receptor, previously linked to inflammation and increased hyperexcitability, to drug-refractory status epilepticus and its therapeutic potential.

Elevated blood purine levels as a biomarker of seizures and epilepsy.

Objective: There is a major unmet need for a molecular biomarker of seizures or epilepsy that lends itself to fast, affordable detection in an easy-to-use point-of-care device. Purines such as adenosine triphosphate and adenosine are potent neuromodulators released during excessive neuronal activity that are also present in biofluids. Their biomarker potential for seizures and epilepsy in peripheral blood has, however, not yet been investigated.

High concordance between hippocampal transcriptome of the mouse intra-amygdala kainic acid model and human temporal lobe epilepsy.

Objective: Pharmacoresistance and the lack of disease-modifying actions of current antiseizure drugs persist as major challenges in the treatment of epilepsy. Experimental models of chemoconvulsant-induced status epilepticus remain the models of choice to discover potential antiepileptogenic drugs, but doubts remain as to the extent to which they model human pathophysiology. The aim of the present study was to compare the molecular landscape of the intra-amygdala kainic acid model of status epilepticus in mice with findings in resected brain tissue from patients with drug-resistant temporal lobe epilepsy (TLE).

P2X7 Receptor-Dependent microRNA Expression Profile in the Brain Following Status Epilepticus in Mice.

The ionotropic ATP-gated P2X7 receptor is an important contributor to inflammatory signaling cascades the release of Interleukin-1β, as well as having roles in cell death, neuronal plasticity and the release of neurotransmitters. Accordingly, there is interest in targeting the P2X7 receptor for the treatment of epilepsy. However, the signaling pathways downstream of P2X7 receptor activation remain incompletely understood.

Characterization of the Expression of the ATP-Gated P2X7 Receptor Following Status Epilepticus and during Epilepsy Using a P2X7-EGFP Reporter Mouse.

Mounting evidence suggests that the ATP-gated P2X7 receptor contributes to increased hyperexcitability in the brain. While increased expression of P2X7 in the hippocampus and cortex following status epilepticus and during epilepsy has been repeatedly demonstrated, the cell type-specific expression of P2X7 and its expression in extra-hippocampal brain structures remains incompletely explored. In this study, P2X7 expression was visualized by using a transgenic mouse model overexpressing P2X7 fused to the fluorescent protein EGFP.

Polyadenylation of mRNA as a novel regulatory mechanism of gene expression in temporal lobe epilepsy.

Temporal lobe epilepsy is the most common and refractory form of epilepsy in adults. Gene expression within affected structures such as the hippocampus displays extensive dysregulation and is implicated as a central pathomechanism. Post-transcriptional mechanisms are increasingly recognized as determinants of the gene expression landscape, but key mechanisms remain unexplored.

The Role of P2X7 Receptor in Alzheimer's Disease.

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease characterized by a progressive cognitive decline associated with global brain damage. Initially, intracellular paired helical filaments composed by hyperphosphorylated tau and extracellular deposits of amyloid-β (Aβ) were postulated as the causing factors of the synaptic dysfunction, neuroinflammation, oxidative stress, and neuronal death, detected in AD patients. Therefore, the vast majority of clinical trials were focused on targeting Aβ and tau directly, but no effective treatment has been reported so far.

ATP Measurement in Cerebrospinal Fluid Using a Microplate Reader.

Imbalance in extracellular ATP levels in brain tissue has been suggested as a triggering factor for several neurological disorders. Here, we describe the most sensitive and reliable technique for monitoring the ATP levels in mice cerebrospinal samples collected by cisterna magna puncture technique and quantified using a microplate reader.

Context-Specific Switch from Anti- to Pro-epileptogenic Function of the P2Y Receptor in Experimental Epilepsy.

Extracellular ATP activates inflammatory responses to tissue injury. It is also implicated in establishing lasting network hyperexcitability in the brain by acting upon independent receptor systems. Whereas the fast-acting P2X channels have well-established roles driving neuroinflammation and increasing hyperexcitability, the slower-acting metabotropic P2Y receptors have received much less attention.

Amyloid Peptide Induced Neuroinflammation Increases the P2X7 Receptor Expression in Microglial Cells, Impacting on Its Functionality.

Alzheimer disease is a neurodegenerative disease characterized by the presence of senile plaques composed of amyloid-β (Aβ) peptide, neurofibrillary tangles, neuronal loss and neuroinflammation. Previous works have revealed that extracellular ATP, through its selective receptor P2X7 (P2X7R), is essential to neuroinflammation and neurotoxicity induced by Aβ. P2X7R is upregulated on microglial cells around the senile plaques.

Nucleotides regulate the common molecular mechanisms that underlie neurodegenerative diseases; Therapeutic implications.

Neurodegenerative diseases (ND) are a heterogeneous group of neurological disorders characterized by a progressive loss of neuronal function which results in neuronal death. Although a specific toxic factor has been identified for each ND, all of them share common pathological molecular mechanisms favouring the disease development. In the final stages of ND, patients become unable to take care of themselves and decline to a total functional incapacitation that leads to their death.

The Neurotoxic Role of Extracellular Tau Protein.

Tauopathies are a class of neurodegenerative diseases associated with the microtubule-associated protein tau, with Alzheimer's disease (AD) being the most prevalent related disorder. Neurofibrillary tangles (NFTs) are one of the neuropathological hallmarks present in the brains of AD patients. Because NFTs are aberrant intracellular inclusions formed by hyperphosphorylated tau, it was initially proposed that phosphorylated and/or aggregated intracellular tau protein was causative of neuronal death.

Haploinsufficient TNAP Mice Display Decreased Extracellular ATP Levels and Expression of Pannexin-1 Channels.

Hypophosphatasia (HPP) is a rare heritable metabolic bone disease caused by hypomorphic mutations in the (in human) or (in mouse) gene, encoding the tissue-nonspecific alkaline phosphatase (TNAP) enzyme. In addition to skeletal and dental malformations, severe forms of HPP are also characterized by the presence of spontaneous seizures. Initially, these seizures were attributed to an impairment of GABAergic neurotransmission caused by altered vitamin B6 metabolism.

The regulation of proteostasis in glial cells by nucleotide receptors is key in acute neuroinflammation.

The disturbances of cellular proteostasis caused by the alteration in the ubiquitin-proteasome system (UPS) have been proposed as a common mechanism underlying several neural pathologies that involve a neuroinflammatory process. As we have previously reported that the nucleotide receptor P2Y purinoceptor 2 (P2YR) regulates the proteasomal catalytic activities, we wonder whether this receptor is involved in the UPS disturbances associated with the neuroinflammation process. With the use of mice expressing a UPS reporter [mice expressing the UPS reporter ubiquitin-green fluorescent protein (UbGFP mice)], we found that LPS-induced acute neuroinflammation status causes a UPS impairment in astrocytes and microglial cells by a mechanism dependent on P2YR.

Neuronal P2X7 Receptor: Involvement in Neuronal Physiology and Pathology.

The proposed presence of P2X7 receptor (P2X7R) in neurons has been the source of some contention. Initial studies suggested an absence of P2X7R mRNA in neurons, and the apparent nonspecificity of the antibodies used to identify P2X7R raised further doubts. However, subsequent studies using new pharmacological and biomolecular tools provided conclusive evidence supporting the existence of functional P2X7Rs in neurons.

Regulation of proteasome activity by P2Y receptor underlies the neuroprotective effects of extracellular nucleotides.

The Ubiquitin-Proteasome System (UPS) is essential for the regulation of the cellular proteostasis. Indeed, it has been postulated that an UPS dysregulation is the common mechanism that underlies several neurological disorders. Considering that extracellular nucleotides, through their selective P2Y receptor (P2YR), play a neuroprotective role in various neurological disorders that course with an UPS impairment, we wonder if this neuroprotective capacity resulted from their ability to modulate the UPS.

Neurodevelopmental alterations and seizures developed by mouse model of infantile hypophosphatasia are associated with purinergic signalling deregulation.

Hypomorphic mutations in the gene encoding the tissue-nonspecific alkaline phosphatase (TNAP) enzyme, ALPL in human or Akp2 in mice, cause hypophosphatasia (HPP), an inherited metabolic bone disease also characterized by spontaneous seizures. Initially, these seizures were attributed to the impairment of GABAergic neurotransmission caused by altered vitamin B6 (vit-B6) metabolism. However, clinical cases in human newborns and adults whose convulsions are refractory to pro-GABAergic drugs but controlled by the vit-B6 administration, suggest that other factors are involved.