Biology subjects

Wegrzynowicz, M.

Publications and source records attributed to Wegrzynowicz, M..

6 recordsLinked to original sources

bioRxiv2025

LOSS OF ARGINASE 2 DISRUPTS STRIATUM-SPECIFIC POLYAMINE HOMEOSTASIS

Arginase converts arginine (Arg) to ornithine (Orn), regulating their availability for the metabolic pathways that utilize these amino acids. The roles of arginase isoenzymes, Arg1 and Arg2, vary by cell type, tissue, and physiological state. In the brain, Arg2 is the predominant isoenzyme, particularly enriched in the striatum, where it localizes to a striatum-specific neuronal population - medium spiny neurons (MSNs). While the precise role of Arg2 in MSNs remains unclear, its loss alters the striatal metabolomic profile, highlighting its metabolic significance. Here, to investigate the basis of these complex metabolic changes, we examined Arg metabolism in Arg2 knockout (Arg2-/-) mice. Targeted analysis of Arg-related metabolites and selected proteins regulating Arg metabolic pathways revealed that Arg2 loss significantly increased Arg levels but did not affect Orn, likely due to compensatory synthesis of Orn from Arg (via arginine:glycine amidinotransferase) and/or proline (via ornithine aminotransferase). Additionally, markers of nitric oxide (NO) production remained unchanged, suggesting that striatal Arg2 is not involved in the regulation of this pathway, a role commonly attributed to arginase. Most notably, Arg2 loss disrupted polyamine homeostasis, shifting the balance toward higher polyamines at the expense of lower ones and altering the expression of polyamine-regulating proteins. These findings highlight Arg2 crucial role in striatal metabolism and its potential relevance to striatum-related disorders. Given that striatal Arg2 impairment has been reported in Huntingtons disease, a neurodegenerative disorder specifically affecting MSNs, understanding its function may provide insights into the pathology.

neuroscience↗

bioRxiv2025

Mitochondrial Calcium Uniporter protects hippocampal CA2 neurons from excitotoxic injury

BackgroundThe hippocampal region CA2, unlike neighboring CA1, is exceptionally resistant to excitotoxicity, although the mechanisms behind this phenotype are unknown. Given the importance of mitochondrial calcium buffering, we investigated whether the Mitochondrial Calcium Uniporter (MCU), recently found to be enriched in CA2, contributes to this resistance. MethodsWe employed immunostaining techniques in rodent brain tissue and organotypic slice cultures to visualize MCU distribution across hippocampal regions under both resting and excitotoxic conditions. Subsequently, we pharmacologically modulated MCU in an organotypic model of hippocampal excitotoxicity to assess its contribution to regional resistance to NMDA. ResultsWe found a strong spatial correlation between resistance to excitotoxic injury and MCU expression. Notably, NMDA exposure resulted in MCU upregulation in CA2, and pharmacological inhibition of MCU sensitized CA2 neurons to excitotoxic damage in a dose-dependent manner, while having minimal effect on the already vulnerable CA1 neurons, which express low MCU levels. ConclusionsMCU is known to exacerbate NMDA-induced cell injury, although our data indicate that CA2 neurons possess unique mitochondrial calcium handling capabilities enabling MCU to support neuroprotection. Our study provides novel insight into mechanisms supporting CA2 resistance to excitotoxic death and emphasizes context-dependent roles of MCU in neuronal injury or survival.

neuroscience↗

bioRxiv2025

Alpha-synuclein aggregation and dopaminergic neuron death in a new mouse model of Parkinson disease expressing human full-length and C-terminally truncated 1-120 alpha-synuclein.

Parkinsons disease (PD) is neuropathologically characterized by the presence of Lewy bodies and Lewy neurites made of aggregated alpha-synuclein (aSyn). Several studies have shown that Lewy bodies contain C-terminally truncated aSyn which is more prone to fibrillation and enhances the aggregation of human full-length aSyn in vitro. Nevertheless, in vivo studies addressing whether and how human C-terminally truncated aSyn may exacerbate the pathological aggregation and toxicity of human full-length aSyn are currently lacking. In the present study we aimed to determine whether the co-expression of human full-length and 1-120 truncated aSyn would enhance human full-length aSyn aggregation and toxicity. To this end we generated and characterized two novel alpha- synuclein mouse models. Specifically, we first produced a mouse line expressing full-length human aSyn under its own promoter (BACo mice) in the absence of endogenous mouse aSyn. Then, the BACo mice were crossed with the previously described MI2 mice, which express human 1-120 truncated aSyn under the control of the tyrosine hydroxylase (TH) promoter on a mouse aSyn null backgroundin order to obtain the MI2BACo mice, which express both human 1-120 truncated and full-length aSyn in a mouse aSyn null background. We found that aSyn aggregation was present and increased with age in both mouse lines but was significantly higher in the MI2BACo mice. These mice exhibited progressive nigrostriatal accumulation of aSyn aggregates which were often composed of full-length and 1-120haSyn, the latter being specifically recognized by using a novel antibody raised against the 1-120haSyn. In addition, we observed that the presence of both truncated and full-length aSyn in MI2BACo mice led to a faster and more pronounced aSyn aggregation which associated with more severe dopaminergic striatal fiber degeneration and nigral neuron loss. Collectively, our results indicate that the expression of human C-terminally truncated aSyn exacerbates human full-length aSyn pathology and support that the novel MI2BACo transgenic mouse line represents an innovative experimental model to study the biological basis of PD and test novel therapeutic approaches.

neuroscience↗

bioRxiv2021

Potent but transient immunosuppression of T-cells is a general feature of erythroid progenitor cells

CD71+ erythroid cells (CECs) have been recently recognized in both neonates and cancer patients as potent immunoregulatory cells. Here, we show that in mice early-stage CECs expand in anemia, have high levels of arginase 2 (ARG2) and reactive oxygen species (ROS). In the spleens of anemic mice, CECs expansion-induced L-arginine depletion suppresses T-cell responses. In humans with anemia, CECs expand and express ARG1 and ARG2 that suppress T-cells IFN-{gamma} production. Moreover, bone marrow CECs from healthy human donors suppress T-cells proliferation. CECs differentiated from peripheral blood mononuclear cells potently suppress T-cell activation, proliferation, and IFN-{gamma} production in an ARG- and ROS-dependent manner. These effects are the most prominent for early-stage CECs (CD71highCD235adim cells). The suppressive properties disappear during erythroid differentiation as more differentiated CECs and mature erythrocytes lack significant immunoregulatory properties. Our studies provide a novel insight into the role of CECs in the immune response regulation. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=179 SRC="FIGDIR/small/427109v2_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@136fbd8org.highwire.dtl.DTLVardef@d05d00org.highwire.dtl.DTLVardef@189baceorg.highwire.dtl.DTLVardef@1472b2b_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2020

CSPα reduces aggregates and rescues striatal dopamine release in αsynuclein transgenic mice

Synuclein aggregation at the synapse is an early event in Parkinsons disease and is associated with impaired striatal synaptic function and dopaminergic neuronal death. The cysteine string protein (CSP) and synuclein have partially overlapping roles in maintaining synaptic function and mutations in each cause neurodegenerative diseases. CSP is a member of the DNAJ/HSP40 family of co-chaperones and like synuclein, chaperones the SNARE complex assembly and neurotransmitter release. Synuclein can rescue neurodegeneration in CSPKO mice. However, whether synuclein aggregation alters CSP expression and function is unknown. Here we show that synuclein aggregation at the synapse induces a decrease in synaptic CSP and a reduction in the complexes that CSP forms with HSC70 and STGa. We further show that viral delivery of CSP rescues in vitro the impaired vesicle recycling in PC12 cells with synuclein aggregates and in vivo reduces synaptic synuclein aggregates restoring normal dopamine release in 1-120hsyn mice. These novel findings reveal a mechanism by which synuclein aggregation alters CSP at the synapse, and show that CSP rescues synuclein aggregation-related phenotype in 1-120hsyn mice similar to the effect of synuclein in CSPKO mice. These results implicate CSP as a potential therapeutic target for the treatment of early-stage PD.

neuroscience↗

bioRxiv2018

Depopulation of α-synuclein aggregates is associated with rescue of dopamine neuron dysfunction and death in a new Parkinson disease model

Parkinsons Disease (PD) is characterized by the presence of -synuclein aggregates known as Lewy bodies and Lewy neurites, whose formation is linked to disease development. The causal relation between -synuclein aggregates and PD is not well understood. We generated a new transgenic mouse line (MI2) expressing human, aggregation-prone truncated 1-120 -synuclein under the control of the tyrosine hydroxylase promoter. MI2 mice exhibit progressive aggregation of -synuclein in dopaminergic neurons of the substantia nigra pars compacta and their striatal terminals. This is associated with a progressive reduction of striatal dopamine release, reduced striatal innervation and significant nigral dopaminergic nerve cell death starting from 6 and 12 months of age, respectively. Overt impairment in motor behavior was found in MI2 mice at 20 months of age, when 50% of dopaminergic neurons are lost. These changes were associated with an increase in the number and density of 20-500nm -synuclein species as shown by dSTORM. Treatment with the oligomer modulator anle138b, from 9-12 months of age, restored striatal dopamine release and prevented dopaminergic cell death. These effects were associated with a reduction of the inner density of -synuclein aggregates and an increase in dispersed small -synuclein species as revealed by dSTORM. The MI2 mouse model recapitulates the progressive dopaminergic deficit observed in PD, showing that early synaptic dysfunction precedes dopaminergic axonal loss and neuronal death that become associated with a motor deficit upon reaching a certain threshold. Our data also provide new mechanistic insight for the effect of anle138bs function in vivo supporting that targeting -synuclein aggregation is a promising therapeutic approach for PD.

neuroscience↗