Biology subjects

Menyhart, A.

Publications and source records attributed to Menyhart, A..

7 recordsLinked to original sources

bioRxiv2026

Direct anti-inflammatory actions of N,N-dimethyltryptamine on microglia are revealed by proteomic profiling and receptor pharmacology

N,N-dimethyltryptamine (DMT) is an endogenous psychedelic tryptamine that has recently emerged as a promising therapeutic candidate for acute ischemic stroke. Although DMT consistently reduces infarct size, attenuates neuroinflammation, and improves functional outcome in experimental stroke, the cellular and receptor mechanisms underlying these effects remain poorly understood. Primary rat microglial cultures were used to examine the direct anti-inflammatory effects of DMT following lipopolysaccharide (LPS)-induced activation. Microglial morphology, phagocytosis, and proteomic alterations were analyzed. Radioligand binding assays determined the affinity of DMT for microglial sigma-1 receptors (Sig-1Rs). Pharmacological inhibition of Sig-1Rs and serotonin (5-HT) receptors was performed to define receptor-specific mechanisms. Translational relevance was evaluated in acute mouse brain slices subjected to mild oxygen-glucose deprivation (mOGD) and anoxic episodes, where microglial activation, spreading depolarizations (SDs), and neuronal injury were assessed. DMT directly suppressed LPS-induced microglial activation, promoted a homeostatic morphology, and reduced phagocytic activity. Proteomic profiling demonstrated that DMT selectively reprogrammed inflammatory pathways by suppressing proteins involved in cytokine and chemokine signaling and oxidative stress while largely preserving arachidonic acid-prostaglandin synthesis. DMT bound microglial Sig-1Rs with micromolar affinity comparable to that reported in whole-brain preparations. Pharmacological inhibition revealed that DMT-induced morphological reprogramming required both Sig-1R and serotonergic signaling, whereas suppression of phagocytosis was largely independent of either receptor pathway. In acute brain slices, DMT attenuated microglial activation, reduced SD propagation and ischemic neuronal injury, and tissue-level neuroprotection depended on serotonergic signaling. DMT directly targets microglia and selectively remodels inflammatory states rather than broadly suppressing microglial activation. The receptor mechanisms underlying its actions are context dependent, with Sig-1R and serotonergic signaling contributing differentially according to the cellular response and experimental model. These findings provide mechanistic insight into the neuroprotective actions of DMT and support its ongoing clinical translation as a potential therapy for ischemic stroke.

neuroscience↗

bioRxiv2026

Senolytic treatment guided by carotid stenosis confers protection against acute ischemic stroke in aged rodents

BackgroundAdvanced age is associated with larger infarct volumes and poorer functional recovery after acute ischemic stroke (AIS). Carotid stenosis is also a common comorbidity in older individuals and often predicts subsequent AIS. However, no age-specific therapy is currently available to protect the aging brain from aggravated ischemic injury. Here, we investigated whether a senolytic approach could improve cerebrovascular status and reduce ischemic brain injury in a comorbid aging model of AIS. MethodsUnilateral common carotid artery occlusion was induced in young and aged rats and served as a diagnostic trigger for chronic senolytic therapy with dasatinib plus quercetin (D+Q). Two weeks later, the distal middle cerebral artery was occluded for 60 min. Compared with untreated animals, infarct size was measured, spreading depolarizations (SDs) were recorded electrophysiologically, cerebral blood flow (CBF) dynamics were monitored by laser speckle contrast imaging, and cerebrovascular senescent cell burden was assessed by immunocytochemistry. Cerebral angiogenesis, central and systemic inflammatory markers, and metabolic status were evaluated using protein arrays and blood glucose measurements. ResultsAged rats developed larger infarcts than young controls, and this age-related increase was attenuated by D+Q treatment. D+Q reduced the higher frequency of SDs observed in the aged ischemic brain. Increased cerebrovascular senescence in aged animals was diminished by D+Q, accompanied by enhanced angiogenesis, although CBF responses to SDs and reperfusion were unchanged. In addition, D+Q modulated central and systemic inflammatory profiles and counteracted age-related metabolic impairment. ConclusionsSenolytic D+Q therapy administered after carotid artery occlusion confers multifaceted protection against subsequent AIS in the aged brain. By targeting fundamental aging mechanisms that exacerbate brain vulnerability to AIS, D+Q enhances the resilience of the aging neurovascular niche. These results identify senolytic therapy as a promising preventive personalized approach to mitigate the disproportionate impact of AIS in older individuals and warrant further investigation.

physiology↗

bioRxiv2025

Gαq/11 signaling counteracts endothelial dysfunction in the brain and protects cognition in aged mice

BackgroundCerebral small vessel disease (cSVD) is a major cause of stroke and dementia, and is associated with increased blood-brain barrier permeability, neuroinflammation, and endothelial dysfunction. Endothelial Gq/11 proteins are involved in vascular tone regulation and have been shown to affect capillary blood flow in the brain. Since factors downstream of activated Gq/11 proteins, such as endothelial NO synthase (eNOS) activity are discussed in cSVD, we wondered whether the brain endothelial Gq/11 signalling pathway might influence cSVD-related pathology. MethodsHere, we generated mice carrying a brain endothelial-specific deletion of the Gq/11 signalling and characterised these mice using different imaging and staining techniques, as well as behaviour tests measuring cognition in adult and aged mice. Immunoblots, electrophysiology, perfusion measurements, and in vitro experiments complemented those techniques. FindingsThe brain endothelial Gq/11 signalling pathway preserves normal vascular reactivity, and its loss resembles mild endothelial dysfunction in the brain. While the vessel structure was maintained in adult mice, a deletion of the Gq/11 signalling led to capillary rarefaction and blood-brain barrier disruption in aged mice. These effects were accompanied by disturbed VEGF signalling and an increase in senescence markers and oxidative stress in the vasculature, culminating in cognitive impairment with increased tau phosphorylation in the cortex and hippocampus, and decreased myelination in the white matter. InterpretationThese findings reflect the main hallmarks of cSVD and demonstrate a protective role of Gq/11 in endothelial cells in ageing. Furthermore, our results show that the combination of cerebral endothelial dysfunction and ageing accelerates cognitive impairment. FundingResearch was supported by grants from the European Research Council (2019-WATCH-810331 to R.N., V.P., and M.S.), the Deutsche Forschungsgemeinschaft (SCHW 416/12-1 to M.S.; WE 6456/1-1 to J.W.; GRK1957 to M.S., H.M.-F., and J.W.), the institutional priority program MI-VascAD of the University of Lubeck (to H.M.-F. and J.W.), and the Marie-Sklodowska-Curie European Unions Horizon 2020 research program (ENTRAIN-813294 to M.S. and J.W.). RESEARCH IN CONTEXTO_ST_ABSEvidence before this studyC_ST_ABSCerebral small vessel disease (cSVD) is associated with advanced age, hypertension, and metabolic diseases. It is considered causal for a substantial part of stroke and dementia cases. Endothelial dysfunction is described as being present in all of the diseases mentioned, and it is discussed to play a role in the development of cSVD. However, most of the evidence is correlational rather than causal, and studies are usually carried out on subjects with an underlying disease for which endothelial dysfunction is a side effect. Added value of this studyHere, we describe a novel brain endothelial signalling pathway that protects against endothelial dysfunction and loss of cerebrovascular reactivity. Without Gq/11 signalling exclusively in the brain endothelium, mice show an impaired ability to increase brain perfusion in response to vasodilatory stimuli, such as neuronal activity. These mice, combined with an older age, develop vessel rarefaction and cognitive dysfunction, which can be explained by increased tau phosphorylation and white matter alteration. Implications of all the available evidenceThese findings, in the context of the existing studies, suggest that endothelial dysfunction per se is sufficient to induce cognitive impairment. They imply that the diagnoses and treatments for diseases associated with cognitive impairment should focus more on a dysfunctional endothelium. The Gq/11 signalling pathway offers a new approach to address treatment endeavours in cSVD and, more broadly, in all diseases associated with a higher risk of vascular dementia and stroke.

neuroscience↗

bioRxiv2024

Nimodipine reduces microglial activation in vitro as evidenced by morphological phenotype, phagocytic activity and next generation RNA sequencing

BackgroundNimodipine, an L-type voltage-gated calcium channel blocker, achieves vasorelaxation by suppressing Ca2+-dependent activation of cerebrovascular smooth muscle cells and is used to prevent delayed ischemic deficit following subarachnoid hemorrhage. Our preclinical drug repurposing studies raised the possibility that nimodipine may attenuate the pro-inflammatory shift in microglial function in response to brain injury. We analyzed the effects of nimodipine on activated microglia at the level of morphological and functional phenotypes, as well as their transcriptomic profile. MethodsLive brain slice preparations from C57BL/6 mice and primary microglia cultures from the cortex of neonatal Sprague Dawley rats were used. Brain slices were subjected to ischemia, and microglial cultures were activated with lipopolysaccharide (LPS; 20 ng/ml). Both preparations were treated with nimodipine (5-10-20 M). The degree of arborization was evaluated in Iba1-stained microglia and expressed as a transformation index (TI). Phagocytic activity of cultured microglia was visualized using fluorescent microbeads. TNF levels in the cultures were measured with ELISA. Total RNA was isolated from microglia and processed for next generation RNA sequencing to determine differentially expressed genes. ResultsNimodipine suppressed the ameboid morphological transformation and increased phagocytosis triggered by ischemia in brain slices and LPS in microglia cultures. At the transcriptional level, LPS resulted in a pro-inflammatory microglial phenotype, affecting the expression of cytokines, the complement system and phagocytosis-related genes. Focusing on the role of calcium in microglial activation, LPS increased RNA transcription of ionotropic purinergic and some TRP channels but decreased the expression of voltage- and ligand-gated calcium channels. In the endoplasmic reticulum, LPS downregulated gene expression of Ryr and IP3 receptors and increased transcription of the SERCA calcium pump gene. Nimodipine co-administered with LPS altered the expression of 110 genes in the opposite direction to LPS activation, of which at least 20 were associated with microglial immune response, 7 with cell adhesion and 2 with autophagy regulation. ConclusionThe effect of nimodipine goes beyond cerebral vasorelaxation. Nimodipine attenuates microglial activation by modulating Ca2+-dependent gene expression involved in intracellular signaling cascades to drive microglial immune responses. Consideration should be given to expanding the medical field of indication of nimodipine.

neuroscience↗

bioRxiv2022

Spreading depolarization causes reperfusion failure after cerebral ischemia

BackgroundDespite successful recanalization to treat acute ischemic stroke, reperfusion failure associated with poor functional outcomes develops in half of the patients. The cause of reperfusion failure remains the subject of intensive research. Here, we explore the possibility that spreading depolarization (SD), a potent ischemic injury mechanism is a significant contributor and reliable predictor of reperfusion failure. MethodsYoung adult male and female C57BL/6 mice (n=69) were anesthetized with isoflurane (0.6-0.9%) and prepared for transcranial optical imaging. After 10 min of baseline, incomplete global forebrain ischemia was induced by transient (45 min) bilateral common carotid artery (CCA) occlusion, followed by 75 min reperfusion. SD and cerebral blood flow (CBF) changes were visualized with intrinsic optical signal imaging and laser speckle contrast imaging. To block SD, the irreversible NMDA receptor antagonist MK801 was applied (0.3 mg/kg, i.p., n=29). Neurological deficit was evaluated at baseline and post-ischemia with a composite Garcia Neuroscore scale. Collaterals of the circle of Willis were examined after loading the vasculature with carbon black ink. Ischemic neuronal injury was evaluated in hematoxylin-eosin-stained brain sections. ResultsSD emerged after ischemia onset in one or both hemispheres under a perfusion threshold (CBF drop to 21.1{+/-}4.6 vs. 33.6{+/-}4.4 %, SD vs. no SD). The failure of later reperfusion (44.4{+/-}12.5 %) was invariably linked to previous ischemic SD. In contrast, reperfusion was adequate (98.9{+/-}7.4 %) in hemispheres devoid of SD during ischemia. CBF reduced below the perfusion threshold of SD, when the P1 segment was absent in the circle of Willis. SD occurrence and the linked reperfusion failure were associated with poor neurologic function, and greater neuronal necrosis. The inhibition of SD with MK801 significantly improved reperfusion. ConclusionsSD occurrence during ischemia impairs later reperfusion, prognosticating poor functional outcomes. The increased likelihood of SD occurrence is predicted by inadequate collaterals.

neuroscience↗

bioRxiv2021

Microglia control cerebral blood flow and neurovascular coupling via P2Y12R-mediated actions

Microglia, the main immunocompetent cells of the brain regulate neuronal function in health and disease, but their contribution to cerebral blood flow (CBF) remained elusive. Here we identify microglia as important modulators of CBF both under physiological conditions and during hypoperfusion. We show that microglia establish direct purinergic contacts with cells in the neurovascular unit that shape cerebral perfusion in both mice and humans. Surprisingly, the absence of microglia or blockade of microglial P2Y12 receptor (P2Y12R) substantially impairs neurovascular coupling in the barrel cortex after whisker stimulation. We also reveal that hypercapnia, which is associated with acidification, induces microglial adenosine production, while depletion of microglia reduces brain pH and impairs hypercapnia-induced vasodilation. Furthermore, the absence or dysfunction of microglia markedly impairs adaptation to hypoperfusion via P2Y12R after transient unilateral common carotid artery occlusion, which is also influenced by CX3CR1-mediated actions. Thus, our data reveal a previously unrecognized role for microglia in CBF regulation with broad implications for common neurological diseases.

neuroscience↗

bioRxiv2020

Malignant astrocyte swelling and impaired glutamate clearance drive the expansion of injurious spreading depolarization foci

Spreading depolarizations (SD) indicate infarct maturation and predict worse clinical outcome in ischemic stroke. We demonstrate here in rodents that brain edema formation upon ischemic stroke impairs astroglial glutamate clearance and increases the tissue area invaded by SD. The cytotoxic glutamate accumulation predisposes an extensive bulk of tissue for a yet undescribed simultaneous depolarization (SiD). We confirm in rat brain slices under hypo-osmotic stress that SiD is the pathological expansion of prior SD foci, is associated with astrocyte swelling and triggers oncotic neuron death. The blockade of astrocytic aquaporin-4 channels and Na+/K+/Cl- co-transporters, or volume-regulated anion channels mitigated slice edema, glutamate accumulation and SiD occurrence. Reversal of slice edema by hyperosmotic treatment counteracted glutamate accumulation and prevented SiD. In contrast, paralysis of astrocyte metabolism or inhibition of astrocyte glutamate uptake reproduced the SiD phenotype. We discuss our results in the light of evidence for SiD in the human cortex. Our results emphasize the need of preventive osmotherapy in ischemic stroke.

neuroscience↗