Understanding the pathogenetic mechanisms underlying altered neuronal function associated with CAMK2B mutations

Calcium/Calmodulin-Dependent Protein Kinase II β Regulates Autophagy Dependent Ferroptosis of Neurons after Cerebral Ischemic Injury by Activating the AREG/JUN/ELAVL1 Pathway

Ferroptosis is an iron-dependent regulatory cell death characterized by lipid peroxidation. The molecular mechanism of calcium/calmodulin-dependent protein kinase II β (CAMK2B) affecting cerebral ischemic injury through autophagy-dependent ferroptosis is still unclear. Here, we aimed to study the regulatory effect of CAMK2B on autophagy-dependent ferroptosis and its effect on cerebral ischemic injury. We found that CAMK2B was significantly upregulated in oxygen and glucose deprivation/recovery (OGD/R)-induced PC12 cells and primary hippocampal neurons. CAMK2B knockdown inhibited OGD/R-induced autophagy-dependent ferroptosis in PC12 cells and primary hippocampal neurons. In addition, CAMK2B was co-localized with amphiregulin (AREG) in PC12 cells, and overexpression of AREG reversed the effect of CAMK2B knockdown on OGD/R-induced autophagy-dependent ferroptosis in PC12 cells and primary hippocampal neurons. Further molecular mechanism studies showed that AREG enhanced the transcriptional activation of embryonic lethal abnormal vision-like 1 (ELAVL1) through Jun Proto-Oncogene (c-Jun), thereby inducing autophagy-dependent ferroptosis in PC12 cells and primary hippocampal neurons. Moreover, CAMK2B was significantly upregulated in the ipsilateral penumbra neurons of cerebral ischemia-reperfusion (I/R) mice, and the level of autophagy-dependent ferroptosis was increased in the brain tissue of I/R mice. Knockdown of CAMK2B alleviated neuronal damage by inhibiting autophagy-dependent ferroptosis in the brain tissue of model mice. This study suggests that CAMK2B plays a key role in regulating neuronal autophagy-dependent ferroptosis, and CAMK2B may be a potential target for the treatment of cerebral I/R injury.

Exacerbated hepatotoxicity in in vivo and in vitro non-alcoholic fatty liver models by biomineralized copper sulfide nanoparticles

Copper sulfide nanoparticles (NPs) synthesized through biomineralization have significant commercial potential as photothermal agents, while the safety evaluation of these NPs, especially for patients with non-alcoholic fatty liver (NAFL), remains insufficient. To explore the differential hepatotoxicity of copper sulfide NPs in NAFL conditions, we synthesized large-sized (LNPs, 15.1 nm) and small-sized (SNPs, 3.5 nm) BSA@Cu2-xS NPs. A NAFL rat model fed with high fat diet (HFD) was successfully established for a 14-day subacute toxicity study by daily repeated administration of BSA@Cu2-xS NPs. Our findings from serum biochemistry and histopathological examinations revealed that copper sulfide at both sizes NPs induced more pronounced liver damage in NAFL rats than rats fed with normal diet. Transcriptome sequencing analysis showed that LNPs activated inflammation and DNA damage repair pathways in the livers of NAFL rats, while SNPs displayed minimal inflammation. A three-dimensional spheroid model of NAFL developed in our in-house cell spheroid culture honeycomb chips demonstrated that LNPs, but not SNPs, triggered a distinct release of inflammatory factors and increased reactive oxygen species through Kupffer cells. These results highlight that NAFL condition exacerbated the hepatotoxicity of BSA@Cu2-xS NPs, with SNPs emerging as safer photothermal agents compared to LNPs, suggesting superior potential for clinical applications.

Ca2+/calmodulin-dependent protein kinase II β decodes ER Ca2+ transients to trigger autophagosome formation

In multicellular organisms, very little is known about how Ca2+ transients on the ER outer surface elicited by autophagy stimuli are sustained and decoded to trigger autophagosome formation. Here, we show that Ca2+/calmodulin-dependent protein kinase II β (CaMKIIβ) integrates ER Ca2+ transients to trigger liquid-liquid phase separation (LLPS) of the autophagosome-initiating FIP200 complex. In response to ER Ca2+ transients, CaMKIIβ is recruited from actin filaments and forms condensates, which serve as sites for the emergence of or interaction with FIP200 puncta. CaMKIIβ phosphorylates FIP200 at Thr269, Thr1127, and Ser1484 to modulate LLPS and properties of the FIP200 complex, thereby controlling its function in autophagosome formation. CaMKIIβ also controls the amplitude, duration, and propagation of ER Ca2+ transients during autophagy induction. CaMKIIβ mutations identified in the neurodevelopmental disorder MRD54 affect the function of CaMKIIβ in autophagy. Our study reveals that CaMKIIβ is essential for sustaining and decoding ER Ca2+ transients to specify autophagosome formation in mammalian cells.

Assessing the Neurodevelopmental Impact of Fluoxetine, Citalopram, and Paroxetine on Neural Stem Cell-Derived Neurons

BACKGROUND/OBJECTIVES

Many pregnant women globally suffer from depression and are routinely prescribed selective serotonin reuptake inhibitors (SSRIs). These drugs function by blocking the re-uptake of serotonin by the serotonin transporter (SERT) into neurons, resulting in its accumulation in the presynaptic cleft. Despite a large amount of research suggesting a potential link to neurodevelopmental disorders in children whose mothers took these drugs during pregnancy, their possible adverse effects are still debated, and results are contradictory. On the other hand, there is an immediate need for improved cell-based models for developmental neurotoxicity studies (DNT) to minimize the use of animals in research.

METHODS

In this study, we aimed to assess the effects of clinically relevant concentrations of paroxetine (PAR), fluoxetine (FLX), and citalopram (CIT)-on maturing neurons derived from human neural stem cells using multiple endpoints.

RESULTS

Although none of the tested concentrations of FLX, CIT, or PAR significantly affected cell viability, FLX (10 µM) exhibited the highest reduction in viability compared to the other drugs. Regarding neurite outgrowth, CIT did not have a significant effect. However, FLX (10 µM) significantly reduced both mean neurite outgrowth and mean processes, PAR significantly reduced mean processes, and showed a trend of dysregulation of multiple genes associated with neuronal development at therapeutic-relevant serum concentrations.

CONCLUSIONS

Transcriptomic data and uptake experiments found no SERT activity in the system, suggesting that the adverse effects of FLX and PAR are independent of SERT.

Developmental origins of Parkinson's disease risk: perinatal exposure to the organochlorine pesticide dieldrin leads to sex-specific DNA modifications in critical neurodevelopmental pathways in the mouse midbrain

Epidemiological studies show that exposure to the organochlorine pesticide dieldrin is associated with an increased risk of Parkinson's disease (PD). Animal studies support a link between developmental dieldrin exposure and increased neuronal susceptibility in the α-synuclein preformed fibril and MPTP models in adult male C57BL/6 mice. In a previous study, we showed that developmental dieldrin exposure was associated with sex-specific changes in DNA modifications within genes related to dopaminergic neuron development and maintenance at 12 wk of age. Here, we used capture hybridization-sequencing with custom baits to interrogate DNA modifications across the entire genetic loci of the previously identified genes at multiple time points-birth, 6, 12, and 36 wk old. We identified largely sex-specific dieldrin-induced changes in DNA modifications at each time point that annotated to pathways important for neurodevelopment, potentially related to critical steps in early neurodevelopment, dopaminergic neuron differentiation, synaptogenesis, synaptic plasticity, and glial-neuron interactions. Despite large numbers of age-specific DNA modifications, longitudinal analysis identified a small number of differential modification of cytosines with dieldrin-induced deflection of epigenetic aging. The sex-specificity of these results adds to evidence that sex-specific responses to PD-related exposures may underly sex-specific differences in disease. Overall, these data support the idea that developmental dieldrin exposure leads to changes in epigenetic patterns that persist after the exposure period and disrupt critical neurodevelopmental pathways, thereby impacting risk of late-life diseases, including PD.

Developmental origins of Parkinson's disease risk: perinatal exposure to the organochlorine pesticide dieldrin leads to sex-specific DNA modifications in critical neurodevelopmental pathways in the mouse midbrain

Epidemiological studies show that exposure to the organochlorine pesticide dieldrin is associated with increased risk of Parkinson's disease (PD). Animal studies support a link between developmental dieldrin exposure and increased neuronal susceptibility in the α-synuclein preformed fibril (α-syn PFF) and MPTP models in adult male C57BL/6 mice. In a previous study, we showed that developmental dieldrin exposure was associated with sex-specific changes in DNA modifications within genes related to dopaminergic neuron development and maintenance at 12 weeks of age. Here, we used capture hybridization-sequencing with custom baits to interrogate DNA modifications across the entire genetic loci of the previously identified genes at multiple time points - birth, 6 weeks, 12 weeks, and 36 weeks old. We identified largely sex-specific dieldrin-induced changes in DNA modifications at each time point that annotated to pathways important for neurodevelopment, potentially related to critical steps in early neurodevelopment, dopaminergic neuron differentiation, synaptogenesis, synaptic plasticity, and glial-neuron interactions. Despite large numbers of age-specific DNA modifications, longitudinal analysis identified a small number of DMCs with dieldrin-induced deflection of epigenetic aging. The sex-specificity of these results adds to evidence that sex-specific responses to PD-related exposures may underly sex-specific differences in disease. Overall, these data support the idea that developmental dieldrin exposure leads to changes in epigenetic patterns that persist after the exposure period and disrupt critical neurodevelopmental pathways, thereby impacting risk of late life diseases, including PD.

Vitamin D, Calbindin, and calcium signaling: Unraveling the Alzheimer's connection

Calcium is a ubiquitous second messenger that is indispensable in regulating neurotransmission and memory formation. A precise intracellular calcium level is achieved through the concerted action of calcium channels, and calcium exerts its effect by binding to an array of calcium-binding proteins, including calmodulin (CAM), calcium-calmodulin complex-dependent protein kinase-II (CAMK-II), calbindin (CAL), and calcineurin (CAN). Calbindin orchestrates a plethora of signaling events that regulate synaptic transmission and depolarizing signals. Vitamin D, an endogenous fat-soluble metabolite, is synthesized in the skin upon exposure to ultraviolet B radiation. It modulates calcium signaling by increasing the expression of the calcium-sensing receptor (CaSR), stimulating phospholipase C activity, and regulating the expression of calcium channels such as TRPV6. Vitamin D also modulates the activity of calcium-binding proteins, including CAM and calbindin, and increases their expression. Calbindin, a high-affinity calcium-binding protein, is involved in calcium buffering and transport in neurons. It has been shown to inhibit apoptosis and caspase-3 activity stimulated by presenilin 1 and 2 in AD. Whereas CAM, another calcium-binding protein, is implicated in regulating neurotransmitter release and memory formation by phosphorylating CAN, CAMK-II, and other calcium-regulated proteins. CAMK-II and CAN regulate actin-induced spine shape changes, which are further modulated by CAM. Low levels of both calbindin and vitamin D are attributed to the pathology of Alzheimer's disease. Further research on vitamin D via calbindin-CAMK-II signaling may provide newer insights, revealing novel therapeutic targets and strategies for treatment.