Biology subjects

Pazarlar, B. A.

Publications and source records attributed to Pazarlar, B. A..

4 recordsLinked to original sources

bioRxiv2026

Spatial and temporal changes in JNJ-64413739 binding to purinergic P2X7 receptor (P2X7R) after status epilepticus induced by intracerebral kainic acid in the rat

Purinergic 2X7 receptor (P2X7R) is considered to play a critical role in neurological diseases, including epilepsy, and has also been proposed as a potential marker for neuroinflammation. This study aimed to validate the binding properties of the novel P2X7R radiotracer, [3H]JNJ-64413739, in rat brain using in vitro autoradiography, and additionally to explore spatial and temporal changes in P2X7R binding levels in a rat model of temporal lobe epilepsy using intrahippocampal administration of kainic acid (KA). Saturation of [3H]JNJ-64413739 to brain sections yielded a KD of approximately 3 nM, with full saturation around 10 nM. The radiotracer was displaced with a structurally different P2X7R ligand, JNJ-47965567, indicating high affinity and specificity to rat P2X7R. In post epileptic rats, region-specific [3H]JNJ-64413739 binding revealed a bilateral increase in the hippocampal formation and its subregions few days after status epilepticus, peaking at day 30, and remained stable at this high level until day 90. Similar temporal profiles were identified in subcortical regions such as the thalamus. Interestingly, no change in binding was observed in the temporal and piriform cortices until day 30 where a dramatic increase occurred. Also, in the corpus callosum, significant increase was detected 30 days after the seizure. These results show that P2X7R binding, likely reflecting inflammation, is increased at delayed time points and exhibit region-specific patterns that is different from acute effects. Our findings suggest that P2X7R may contribute to sustained neuroinflammation and may be involved in those changes leading to epileptogenesis and the development of chronic epilepsy. Highlights[3H]JNJ-64413739 binds specifically to the purinergic P2X7 receptor (P2X7R) and saturates in the rat brain. P2X7R binding increases in a region- and time-dependent manner following status epilepticus. P2X7R binding remains elevated during chronic epilepsy in all examined brain regions. P2X7R is considered a link between early seizures and sustained neuroinflammation and epileptogenesis.

neuroscience↗

bioRxiv2026

5-MOP: a novel and selective colony stimulating factor-1 receptor (CSF1R) radiotracer

Colony stimulating factor 1 receptor (CSF1R) is a tyrosine kinase receptor that is expressed exclusively in microglia within the CNS. Its endogenous ligands, colony stimulating factor-1 (CSF1) and interleukin-34 (IL-34), are released from neurons, positioning CSF1R as a key mediator receptor of neuron-glia communication. CSF1R is considered not only a potential drug target, but also a biomarker of neuroinflammation. From that perspective, selective radioligands for neuroimaging are of great interest for imaging neuroinflammation and determining drug occupancy. In this study, we have validated the binding characteristics of a CSF1R inhibitor, 4-((5-MethOxy-6-((5-methoxypyridin-2-yl)methoxy)pyridin-3-yl)methyl)-2-(1-methyl-1H-pyrazol-4-yl)pyrimidine (5-MOP) as a novel CSF1R radioligand, by performing in vitro saturation binding experiments in human and murine tissues. 5-MOP was found to be selective for CSF1R among a broad range of kinases. Autoradiography revealed that [3H]5-MOP binds with high affinity (KD = 9.8 nM) to a single saturable binding site in human meningioma tissues, and this binding was displaced with known CSF1R inhibitors, including CPPC, sCSF1inh and GW-2580. In contrast, CPPC, which has been extensively used as a CSF1R radioligand showed substantial cross-reactivity to other brain kinases, including Trk A/B/C, and [3H]CPPC could only be displaced with CPPC itself, not by other ligands, including 5-MOP. These results identify [3H]5-MOP as the most selective radioligand currently available, enabling accurate detection of drug occupancy and activated microglia. Significance of the studyThis study identifies and validates a novel selective radioligand that binds CSF1R with high selectivity and low nanomolar affinity. Because CSF1R is selectively expressed in activated microglia, this radioligand could be useful for detecting neuroinflammatory activity.

neuroscience↗

bioRxiv2025

T-401 binding to monoacylglycerol lipase (MAGL) in the brains of patients and mice with temporal lobe epilepsy

Monoacylglycerol lipase (MAGL) inhibitors are considered as drug candidates for epilepsy. In order to determine the level of MAGL and evaluate changes in the epileptic brain, we have validated and used autoradiography and the MAGL radiotracer [3H]T-401 on resected temporal neocortex specimens obtained from patients with temporal lobe epilepsy and in brains from mice with chronic reoccurring seizures. Saturation experiments revealed a KD around 4 nM for the human temporal cortex and 7 nM for the mouse brain. In the human brain, binding of [3H]T-401 was detected mostly in the grey matter, and in the subcortical white matter in lower amounts. The levels were strongly correlated in the two cortical compartments. The level of [3H]T-401 binding in the human temporal cortex varied about a 4-fold among the patients, but was not correlated to either epilepsy duration or the age of the patients. In the epileptic mouse brain, a significant reduction was observed bilaterally in the hippocampus, as well as in other cortical regions, including the temporal cortex. Interestingly, a highly significant negative correlation was seen between MAGL and binding to the translocator protein 18 kDa (TSPO) expressed in glia. These data support the presence of MAGL in neuronal and non-neuronal cells, and indicate that MAGL levels in the brains of either patients with epilepsy or mice after intra-hippocampal kainite injection are reduced not only in the epileptic zone in the hippocampus, but more widespread in the brain.

neuroscience↗

bioRxiv2025

Astroglial TNFR2 signaling regulates hippocampal synaptic function and plasticity in a sex dependent manner

Astrocytes participate in synaptic transmission and plasticity through tightly regulated, bidirectional communication with pre- and post-synaptic neurons, as well as microglia and oligodendrocytes. A key component of astrocyte-mediated synaptic regulation is the cytokine tumor necrosis factor (TNF). TNF signals via two cognate receptors, TNFR1 and TNFR2, both expressed in astrocytes. While TNFR1 signaling in astrocytes has been long demonstrated to be necessary for physiological synaptic function, the role of astroglial TNFR2 has never been explored. Here, we demonstrate that astroglial TNFR2 is essential for maintaining hippocampal synaptic function and plasticity in physiological conditions. Indeed, GfapcreERT2:Tnfrsf1bfl/fl mice with selective ablation of TNFR2 in astrocytes exhibited dysregulated expression of neuronal and glial proteins (e.g., SNARE complex molecules, glutamate receptor subunits, glutamate transporters) essential for hippocampal synaptic transmission and plasticity. Hippocampal astrocytes sorted from GfapcreERT2:Tnfrsf1bfl/fl mice displayed downregulation of genes and pathways implicated in synaptic plasticity, as well as astrocyte-neuron and astrocyte-oligodendrocyte communication. These alterations were accompanied by increased glial reactivity and impaired astrocyte calcium dynamics, and ultimately translated into functional deficits, specifically impaired long-term potentiation (LTP) and cognitive functions. Notably, male GfapcreERT2:Tnfrsf1bfl/fl mice exhibited more pronounced hippocampal synaptic and cellular alterations, suggesting sex-dependent differences in astroglial TNFR2 regulation of synaptic function. Together, these findings indicate that TNFR2 signaling in astrocytes is essential for proper astrocyte-neuron communication at the basis of synaptic function, and that this is regulated in a sex-dependent manner.

neuroscience↗