Regulatory role of calpain in neuronal death

Cytotoxicity by endocrine disruptors through effects on ER Ca2+ transporters, aberrations in Ca2+ signalling pathways and ER stress

Concerns regarding man-made organic chemicals pervading our ecosystem and having adverse and detrimental effects upon organisms, including man, have now been studied for several decades. Since the 1970s, some environmental pollutants were identified as having endocrine disrupting affects. These endocrine disrupting chemicals (EDC) were initially shown to have estrogenic or anti-estrogenic properties and some were also shown to bind to a variety of hormone receptors. However, since the 1990s it has also been identified that many of these EDC additionally, have the ability of causing abnormal alterations in Ca2+ signalling pathways (also commonly involved in hormone signalling), leading to exaggerated elevations in cytosolic [Ca2+] levels, that is known to cause activation of a number of cell death pathways. The major emphasis of this review is to present a personal perspective of the evidence for some types of EDC, specifically alkylphenols and brominated flame retardants (BFRs), causing direct effects on Ca2+ transporters (mainly the SERCA Ca2+ ATPases), culminating in acute cytotoxicity and cell death. Evidence is also presented to indicate that this Ca2+ATPase inhibition, which leads to abnormally elevated cytosolic [Ca2+], as well as a decreased luminal ER [Ca2+], which triggers the ER stress response, are both involved in acute cytotoxicity.

Licochalcone A attenuates NMDA-induced neurotoxicity

This study investigates the effect of Licochalcone A (Lico-A), a flavonoid from licorice roots known for its anti-inflammatory, anti-cancer, and antioxidant properties, on NMDA-induced neurotoxicity in primary cultured rat hippocampal neurons. The study measured cell survival following NMDA and Lico-A exposure, revealing that Lico-A at a 2.5 μg/ml significantly improved cell viability, countering the detrimental effects of NMDA. The study also analyzed synaptic changes by examining both postsynaptic density 95 (PSD95) and synaptophysin-targeted imaging, showing that Lico-A treatment resulted in a significant increase in synaptic puncta, contrasting with the reduction observed under NMDA exposure. Furthermore, levels of phosphorylated mixed lineage kinase domain-like pseudokinase (P-MLKL) and phosphorylated receptor-interacting serine/threonine-protein kinase 3 (P-RIP3), key necroptosis regulators, were measured using Western blotting. The results showed an increase in P-MLKL and P-RIP3 in neurons exposed to NMDA, which was reduced following Lico-A treatment. The response of astrocyte and microglia was also evaluated by immunostaining for glial fibrillary acidic protein (GFAP), ionized calcium-binding adaptor molecule 1 (IBA-1) and tumor necrosis factor alpha (TNF-α). These markers exhibited heightened expression in the NMDA group, which was substantially reduced by Lico-A treatment. These findings suggest that Lico-A has neuroprotective effects against NMDA-induced neurotoxicity, potentially contributing to synaptic preservation, inhibition of neuronal necroptosis, and modulation of glial activation. Therefore, Lico-A shows promise as a neuroprotective agent for conditions associated with NMDA-related neurotoxicity.

Trauma in Neonatal Acute Brain Slices Alters Calcium and Network Dynamics and Causes Calpain-Mediated Cell Death

Preparing acute brain slices produces trauma that mimics severe penetrating brain injury. In neonatal acute brain slices, the spatiotemporal characteristics of trauma-induced calcium dynamics in neurons and its effect on network activity are relatively unknown. Using multiphoton laser scanning microscopy of the somatosensory neocortex in acute neonatal mouse brain slices (P8-12), we simultaneously imaged neuronal Ca2+ dynamics (GCaMP6s) and cytotoxicity (propidium iodide or PI) to determine the relationship between cytotoxic Ca2+ loaded neurons (GCaMP-filled) and cell viability at different depths and incubation times. PI+ cells and GCaMP-filled neurons were abundant at the surface of the slices, with an exponential decrease with depth. Regions with high PI+ cells correlated with elevated neuronal and neuropil Ca2+ The number of PI+ cells and GCaMP-filled neurons increased with prolonged incubation. GCaMP-filled neurons did not participate in stimulus-evoked or seizure-evoked network activity. Significantly, the superficial tissue, with a higher degree of trauma-induced injury, showed attenuated seizure-related neuronal Ca2+ responses. Calpain inhibition prevented the increase in PI+ cells and GCaMP-filled neurons in the deep tissue and during prolonged incubation times. Isoform-specific pharmacological inhibition implicated calpain-2 as a significant contributor to trauma-induced injury in acute slices. Our results show a calpain-mediated spatiotemporal relationship between cell death and aberrant neuronal Ca2+ load in acute neonatal brain slices. Also, we demonstrate that neurons in acute brain slices exhibit altered physiology depending on the degree of trauma-induced injury. Blocking calpains may be a therapeutic option to prevent acute neuronal death during traumatic brain injury in the young brain.

The underlying mechanism of calcium toxicity-induced autophagic cell death and lysosomal degradation in early stage of cerebral ischemia

Cerebral ischemia is the important cause of worldwide disability and mortality, that is one of the obstruction of blood vessels supplying to the brain. In early stage, glutamate excitotoxicity and high level of intracellular calcium (Ca2+) are the major processes which can promote many downstream signaling involving in neuronal death and brain tissue damaging. Moreover, autophagy, the reusing of damaged cell organelles, is affected in early ischemia. Under ischemic conditions, autophagy plays an important role to maintain energy of the brain and its function. In the other hand, over intracellular Ca2+ accumulation triggers excessive autophagic process and lysosomal degradation leading to autophagic process impairment which finally induce neuronal death. This article reviews the association between intracellular Ca2+ and autophagic process in acute stage of ischemic stroke.

New perspective for Calpain-Mediated regulation of meat Quality: Unveiling the impact on mitochondrial pathway apoptosis in post-mortem

While calpain's role in myofibrillar protein degradation is well-established, its impact on post-mortem apoptosis remains fully elucidated. This study aimed to examine how calpain influences the mitochondrial apoptotic pathway in post-mortem muscle cells and assess its potential impact on chicken tenderness. The findings indicate that the calpain inhibitor treatment could decelerate the rate of lysosome destruction in post-mortem chicken, which is a crucial factor in delaying the mitochondrial apoptotic pathway. Subsequently, this inhibition enhanced the mitochondrial membrane's stability and suppressed the apoptosis-inducing factor Cyt c release into the sarcoplasm. The Western blot results in a greater myofibrillar protein degradation degree in the caspase inhibitor samples compared to the calpain inhibitor samples. Interestingly, the two groups had no significant difference in shear force. Based on these reasons, a novel perspective was introduced in this paper: Calpain could affect the change in meat tenderness by regulating mitochondrial apoptosis in the post-mortem period.

Cell-free fat extract promotes axon regeneration and retinal ganglion cells survival in traumatic optic neuropathy

Injuries to axons within the central nervous system (CNS) pose a substantial clinical challenge due to their limited regenerative capacity. This study investigates the therapeutic potential of Cell-free fat extract (CEFFE) in CNS injury. CEFFE was injected intravitreally after the optic nerve was crushed. Two weeks post-injury, quantification of regenerated axons and survival rates of retinal ganglion cells (RGCs) were performed. Subsequently, comprehensive gene ontology (GO) an-notation elucidated the cellular origins and functional attributes of CEFFE components. Molecular mechanisms underlying CEFFE's therapeutic effects were explored through Western blotting (WB). Additionally, levels of inflammatory factors within CEFFE were determined using enzyme-linked immunosorbent assay (ELISA), and histological staining of microglia was conducted to assess its impact on neuroinflammation. CEFFE demonstrated a significant capacity to promote axon re-generation and enhance RGCs survival. GO annotation revealed the involvement of 146 proteins within CEFFE in axonogenesis and neurogenesis. WB analysis unveiled the multifaceted pathways through which CEFFE exerts its therapeutic effects. Elevated levels of inflammatory factors were detected through ELISA, and CEFFE exhibited a modulatory effect on microglial activation in the retinal tissue following optic nerve crush (ONC). The present study highlights the therapeutic promise of CEFFE in the management of CNS injuries, exemplified by its ability to foster axon regeneration and improve RGCs survival.

Post-Anesthesia Cognitive Dysfunction in Mice Is Associated with an Age-Related Increase in Neuronal Intracellular [Ca2+]-Neuroprotective Effect of Reducing Intracellular [Ca2+]: In Vivo and In Vitro Studies

Background: Postoperative cognitive dysfunction (POCD) is a common disorder after general anesthesia in elderly patients, the precise mechanisms of which remain unclear. Methods: We investigated the effect of isoflurane with or without dantrolene pretreatment on intracellular calcium concentration ([Ca2+]i), reactive oxygen species (ROS) production, cellular lactate dehydrogenase (LDH) leak, calpain activity, and cognitive function using the Morris water maze test of young (3 months), middle-aged (12-13 months), and aged (24-25 months) C57BL6/J mice. Results: Aged cortical and hippocampal neurons showed chronically elevated [Ca2+]i compared to young neurons. Furthermore, aged hippocampal neurons exhibited higher ROS production, increased LDH leak, and elevated calpain activity. Exposure to isoflurane exacerbated these markers in aged neurons, contributing to increased cognitive deficits in aged mice. Dantrolene pretreatment reduced [Ca2+]i for all age groups and prevented or significantly mitigated the effects of isoflurane on [Ca2+]i, ROS production, LDH leak, and calpain activity in aged neurons. Dantrolene also normalized or improved age-associated cognitive deficits and mitigated the cognitive deficits caused by isoflurane. Conclusions: These findings suggest that isoflurane-induced cytotoxicity and cognitive decline in aging are linked to disruptions in neuronal intracellular processes, highlighting the reduction of [Ca2+]i as a potential therapeutic intervention.

Brief and diverse excitotoxic insults cause an increase in neuronal nuclear membrane permeability in the neonatal brain

Neuronal swelling after excitotoxic insults is implicated in neuronal injury and death in the developing brain, yet mitigating brain edema with osmotic and surgical interventions yields poor clinical outcomes. Importantly, neuronal swelling and its downstream consequences during early brain development remain poorly investigated. Using multiphoton Ca2+ imaging in vivo (P12-17) and in acute brain slices (P8-12), we explored Ca2+-dependent downstream effects after neuronal cytotoxic edema. We observed the translocation of cytosolic GCaMP6s into the nucleus of a subpopulation of neurons minutes after various excitotoxic insults. We used automated morphology-detection algorithms for neuronal segmentation and quantified the nuclear translocation of GCaMP6s as the ratio of nuclear and cytosolic intensity (N/C ratio). Elevated neuronal N/C ratios were correlated to higher Ca2+ loads and could occur independently of neuronal swelling. Electron microscopy revealed that the nuclear translocation was associated with increased nuclear pore size. Inhibiting calpains prevented elevated N/C ratios and neuronal swelling. Thus, our results indicate altered nuclear transport in a subpopulation of neurons shortly after injury in the developing brain, which can be used as an early biomarker of acute neuronal injury.

Necroptosis involved in sevoflurane-induced cognitive dysfunction in aged mice by activating NMDA receptors increasing intracellular calcium

Perioperative neurocognitive disorders are a common surgical and postanesthesia complication. Necroptosis contributes to the emergence of various neurological disorders. We conjecture that cognitive impairment is associated with necroptosis of hippocampal neurons, which is mediated by NMDA receptors leading to cytoplasmic calcium imbalance. C57BL/6 J male mice ( 18 months) were randomly divided into the C ( control group), S ( sevoflurane group), S+M ( sevoflurane plus the NMDA receptor antagonist memantine group) and S+N ( sevoflurane plus necrostatin-1) group. We exposed the mice to 3% sevoflurane for 2 h a day for three consecutive days in the S, S+M and S+N groups. Memantine ( 20 mg/kg) or Nec-1 ( 10 mg/kg) was injected intraperitoneally 1 h before sevoflurane anesthesia in the S+M or S+N group. We used the animal behavior tests to evaluate the cognitive function. Pathological damage, the rate of necroptosis, [Ca2+]i, and the expression of necroptosis-related proteins were evaluated. The cognitive function tests, pathological damage, the rate of necroptosis, the expression of necroptosis-related proteins, NMDAR2A and NMDAR2B were significantly different in the S group ( P < 0.05). Alleviated pathological damage, decreased the rate of necroptosis and down-regulated the expression of necroptosis-related proteins occurred in the S+M and S+N group ( P < 0.05). The lower elevated [Ca2+]i, expression of NMDAR2A and NMDAR2B were found in the S+M group. Our findings highlighted sevoflurane-induced cognitive dysfunction is associated with an imbalance in cytoplasmic calcium homeostasis by activating NMDA receptors, which causes hippocampus neurons to undergo necroptosis and ultimately affects cognitive performance in aged mice.

Downregulation of NHE1 expression attenuates apoptosis of primary hippocampal neurons of an epilepsy model through the calpain-1 pathway

OBJECTIVE

Na(+)/H(+) exchanger isoform 1 (NHE1), a membrane protein that regulates intracellular pH, is abundantly expressed in brain tissues. It is associated with pathophysiologies in several brain diseases. The present study aimed to investigate the effects of NHE1 on the apoptosis of primary neurons of an epilepsy model.

METHODS

Primary hippocampal neurons were cultured in an Mg2+-free medium to establish an epilepsy cell model. Designed shNHE1 lentivirus was used to silence NHE1 level in primary neurons. Nonselective pharmacological inhibitor MDL-28170 (20 μmol/L) was used to inhibit calpain-1 protein in neurons treated with Mg2+-free medium. The expression levels of NHE1 and calpain-1, intracellular Ca2+ (Ca2+i) and H+ (H+i) levels, and the expression levels of apoptosis-related proteins Bcl-2 and Bax were detected in neurons. TUNEL staining was performed to determine apoptosis in different groups.

RESULTS

NHE1 expression was increased in primary neurons treated with an Mg2+-free medium, and it was correlated with increased expression of calpain-1 and cell apoptosis. Neurons from the in vitro epilepsy model showed significantly decreased Bcl-2 protein expression and significantly increased Bax protein expression. In the presence of LV-shNHE1 and the calpain-1 inhibitor MDL-28170, the changes in the expression of apoptosis-related proteins Bcl-2 and Bax were blocked in the epileptic model, and the percentage of apoptotic neurons among neurons from the in vitro epilepsy model was significantly decreased. The increase in calpain-1 expression was suppressed by LV-shNHE1; however, the inhibition of calpain-1 did not affect NHE1 expression.

CONCLUSION

These results demonstrate that NHE1 participates in the promotion of neuronal apoptosis of epilepsy model in vitro through the calpain-1 pathway. Downregulation of NHE1 expression could exert a neuroprotective effect on epilepsy.

Melatonin mitigates type 1 diabetes-aggravated cerebral ischemia-reperfusion injury through anti-inflammatory and anti-apoptotic effects

INTRODUCTION

Cerebral ischemia and diabetes mellitus (DM) are common diseases that often coexist and interact with each other. DM doubles the risk of ischemic stroke, and cerebral ischemia causes stress-induced hyperglycemia. Most experimental stroke studies used healthy animals. Melatonin is neuroprotective against cerebral ischemia-reperfusion injury (CIRI) in non-DM, normoglycemic animals through anti-oxidant effect, anti-inflammation, and anti-apoptosis. Previous studies have also reported a negative correlation between hyperglycemia and urinary melatonin metabolite.

OBJECTIVES

The present study investigated the effects of type 1 DM (T1DM) on CIRI in rats and the role of melatonin against CIRI in T1DM animals.

RESULTS

Our results revealed that T1DM aggravated CIRI, leading to greater weight loss, increased infarct volume, and worse neurological deficit. T1DM aggravated the post-CIRI activation of nuclear factor kappa B (NF-κB) pathway and increase in pro-apoptotic markers. A single intraperitoneal injection of melatonin at 10 mg/kg given 30 min before ischemia onset attenuated CIRI in T1DM rats, resulting in less weight loss, decreased infarct volume, and milder neurological deficit when compared with the vehicle group. Melatonin treatment achieved anti-inflammatory and anti-apoptotic effects with reduced NF-κB pathway activation, reduced mitochondrial cytochrome C release, decreased calpain-mediated spectrin breakdown product (SBDP), and decreased caspase-3-mediated SBDP. The treatment also led to fewer iNOS+ cells, milder CD-68+ macrophage/microglia infiltration, decreased TUNEL+ apoptotic cells, and better neuronal survival.

CONCLUSIONS

T1DM aggravates CIRI. Melatonin treatment is neuroprotective against CIRI in T1DM rats via anti-inflammatory and anti-apoptotic effects.

RIP3/MLKL regulates necroptosis via activating 4EBP1-eIF4E pathway

OBJECTIVES

Necroptosis is a cell death type mediated by receptor interacting protein 3 (RIP3)/mixed lineage kinase domain-like protein (MLKL). It has been reported that mammalian target of rapamycin plays a regulatory role in necroptosis. Eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1)-eukaryotic initiation factor 4E (eIF4E) pathway is a key down streamer of mammalian target of rapamycin. However, whether 4EBP1-eIF4E pathway is involved in necroptosis is still unknown. This study aims to investigate the changes of 4EBP1-eIF4E pathway in necroptosis.

METHODS

TNF-α/SM-164/Z-VAD-FMK (TSZ), a necroptosis inducer, was used to induce necroptosis in murine fibroblastoid cell line L929. Cell necrosis was observed under an optical microscope. Then, TSZ was added to L929 cells with RIP3 and MLKL gene knockout. Propidium iodide (PI) staining was used to observe cell necrosis. Real-time fluorescence quantitative PCR and Western blotting were used to determine the mRNA and protein expression of 4EBP1 and eIF4E, respectively.

RESULTS

After treating L929 cells with TSZ, the number of necrotic cells was increased, the mRNA and protein expression levels of 4EBP1 were significantly downregulated, and the ratio of phosphorylated 4EBP1 (p-4EBP1) to 4EBP1 was increased (P<0.05 or P<0.01); the mRNA expression level of eIF4E was significantly upregulated, and the ratio of phosphorylated eIF4E (p-eIF4E) to eIF4E was increased (both P<0.01). After knocking out RIP3 and MLKL in L929 cells, PI positive necrotic cells were significantly reduced, the mRNA and protein expression levels of 4EBP1 were significantly upregulated, and the ratio of p-4EBP1 to 4EBP1 was decreased (P<0.05 or P<0.01); the mRNA expression level of eIF4E was significantly downregulated, and the ratio of p-eIF4E to eIF4E was decreased (both P<0.01).

CONCLUSIONS

4EBP1-eIF4E pathway is activated in the RIP3/MLKL mediated-necroptosis.

Prevention of noise-induced hearing loss by calpain inhibitor MDL-28170 is associated with upregulation of PI3K/Akt survival signaling pathway

Introduction

Noise-induced calcium overload in sensory hair cells has been well documented as an early step in the pathogenesis of noise-induced hearing loss (NIHL). Alterations in cellular calcium homeostasis mediate a series of cellular events, including activation of calcium-dependent protein kinases and phosphatases. Using cell-membrane- and blood-brain-barrier-permeable calpain-1 (μ-calpain) and calpain-2 (m-calpain) inhibitor MDL-28170, we tested the involvement of calpains, a family of calcium-dependent cysteine proteases, and the potential of MDL-28170 in preventing NIHL.

Methods

CBA/J mice at the age of 12 weeks were exposed to broadband noise with a frequency spectrum from 2-20 kHz for 2 h at 101 dB sound pressure level to induce permanent hearing loss as measured by auditory brainstem response and distortion product otoacoustic emissions. Morphological damage was assessed by quantification of remaining sensory hair cells and inner hair cell synapses 2 weeks after the exposure.

Results

MDL-28170 treatment by intraperitoneal injection significantly attenuated noise-induced functional deficits and cochlear pathologies. MDL-28170 treatment also prevented noise-induced cleavage of alpha-fodrin, a substrate for calpain-1. Furthermore, MDL-28170 treatment prevented reduction of PI3K/Akt signaling after exposure to noise and upregulated p85α and p-Akt (S473) in outer hair cells.

Discussion

These results indicate that noise-induced calpain activation negatively regulates PI3K/Akt downstream signaling, and that prevention of NIHL by treatment with MDL-28170 is associated with upregulation of PI3K/Akt survival signaling pathways.

An isoform of the giant protein titin is a master regulator of human T lymphocyte trafficking

Response to multiple microenvironmental cues and resilience to mechanical stress are essential features of trafficking leukocytes. Here, we describe unexpected role of titin (TTN), the largest protein encoded by the human genome, in the regulation of mechanisms of lymphocyte trafficking. Human T and B lymphocytes express five TTN isoforms, exhibiting cell-specific expression, distinct localization to plasma membrane microdomains, and different distribution to cytosolic versus nuclear compartments. In T lymphocytes, the LTTN1 isoform governs the morphogenesis of plasma membrane microvilli independently of ERM protein phosphorylation status, thus allowing selectin-mediated capturing and rolling adhesions. Likewise, LTTN1 controls chemokine-triggered integrin activation. Accordingly, LTTN1 mediates rho and rap small GTPases activation, but not actin polymerization. In contrast, chemotaxis is facilitated by LTTN1 degradation. Finally, LTTN1 controls resilience to passive cell deformation and ensures T lymphocyte survival in the blood stream. LTTN1 is, thus, a critical and versatile housekeeping regulator of T lymphocyte trafficking.

Emerging Epidemiological Data on Rare Intellectual Disability Syndromes from Analyzing the Data of a Large Iranian Cohort

BACKGROUND

Intellectual disability (ID) is a genetically heterogeneous condition, and so far, 1679 human genes have been identified for this phenotype. Countries with a high rate of parental consanguinity, such as Iran, provide an excellent opportunity to identify the remaining novel ID genes, especially those with an autosomal recessive (AR) mode of inheritance. This study aimed to investigate the most prevalent ID genes identified via next-generation sequencing (NGS) in a large ID cohort at the Genetics Research Center (GRC) of the University of Social Welfare and Rehabilitation Sciences.

METHODS

First, we surveyed the epidemiological data of 619 of 1295 families in our ID cohort, who referred to the Genetics Research Center from all over the country between 2004 and 2021 for genetic investigation via the NGS pipeline. We then compared our data with those of several prominent studies conducted in consanguineous countries. Data analysis, including cohort data extraction, categorization, and comparison, was performed using the R program version 4.1.2.

RESULTS

We categorized the most common ID genes that were mutated in more than two families into 17 categories. The most common syndromic ID in our cohort was AP4 deficiency syndrome, and the most common non-syndromic autosomal recessive intellectual disability (ARID) gene was ASPM. We identified two unrelated families for the 36 ID genes. We found 14 genes in common between our cohort and the Arab and Pakistani groups, of which three genes (AP4M1, AP4S1, and ADGRG1) were repeated more than once.

CONCLUSION

To date, there has been no comprehensive targeted NGS platform for the detection of ID genes in our country. Due to the large sample size of our study, our data may provide the initial step toward designing an indigenously targeted NGS platform for the diagnosis of ID, especially common ARID in our population.

A bibliometric analysis of apoptosis in glaucoma

Background

Glaucoma is the first irreversible and second blindness disease, which is characterized by the death of retinal ganglion cells (RGCs) and degeneration of the optic nerve. Previous works have indicated that apoptosis is the main reason for RGC death in glaucoma. Although many studies have investigated the mechanism of apoptosis and different strategies targeting apoptosis to protect the RGCs and finally recover the impaired vision in the glaucoma. However, the global trend and hotspots of apoptosis in glaucoma have not been well illustrated and discussed.

Methods

Documents were extracted from the Web of Science Core Collection on November 2, 2022. We selected articles and reviews published in English from January 1, 1999 to November 1, 2022 to perform visual analysis and statistical analysis of countries, institutions, authors, references and keywords by VOSviewer 1.6.18 and CiteSpace 5.8.

Results

The publications about apoptosis in glaucoma show an increasing trend over time. Besides, the authors, institutions in the US and China published the most numbers of articles with the highest citation, which may be leading the research in the field of apoptosis in glaucoma. Last, series of advanced research results, technology and treatment for glaucoma, such as the discovery of key regulatory mechanisms on RGC apoptosis are emerging and will provide precise strategies for the treatment of glaucoma.

Conclusion

This research will broaden our comprehension about the role of apoptosis in the process of glaucoma, and provide guidelines for us in basic research and disease treatment in the further.

From 2D to 3D: Development of Monolayer Dopaminergic Neuronal and Midbrain Organoid Cultures for Parkinson's Disease Modeling and Regenerative Therapy

Parkinson's Disease (PD) is a prevalent neurodegenerative disorder that is characterized pathologically by the loss of A9-specific dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) of the midbrain. Despite intensive research, the etiology of PD is currently unresolved, and the disease remains incurable. This, in part, is due to the lack of an experimental disease model that could faithfully recapitulate the features of human PD. However, the recent advent of induced pluripotent stem cell (iPSC) technology has allowed PD models to be created from patient-derived cells. Indeed, DA neurons from PD patients are now routinely established in many laboratories as monolayers as well as 3D organoid cultures that serve as useful toolboxes for understanding the mechanism underlying PD and also for drug discovery. At the same time, the iPSC technology also provides unprecedented opportunity for autologous cell-based therapy for the PD patient to be performed using the patient's own cells as starting materials. In this review, we provide an update on the molecular processes underpinning the development and differentiation of human pluripotent stem cells (PSCs) into midbrain DA neurons in both 2D and 3D cultures, as well as the latest advancements in using these cells for drug discovery and regenerative medicine. For the novice entering the field, the cornucopia of differentiation protocols reported for the generation of midbrain DA neurons may seem daunting. Here, we have distilled the essence of the different approaches and summarized the main factors driving DA neuronal differentiation, with the view to provide a useful guide to newcomers who are interested in developing iPSC-based models of PD.

The regulatory role of Pin1 in neuronal death

Regulated cell death predominantly involves apoptosis, autophagy, and regulated necrosis. It is vital that we understand how key regulatory signals can control the process of cell death. Pin1 is a cis-trans isomerase that catalyzes the isomerization of phosphorylated serine or threonine-proline motifs of a protein, thereby acting as a crucial molecular switch and regulating the protein functionality and the signaling pathways involved. However, we know very little about how Pin1-associated pathways might play a role in regulated cell death. In this paper, we review the role of Pin1 in regulated cell death and related research progress and summarize Pin1-related pathways in regulated cell death. Aside from the involvement of Pin1 in the apoptosis that accompanies neurodegenerative diseases, accumulating evidence suggests that Pin1 also plays a role in regulated necrosis and autophagy, thereby exhibiting distinct effects, including both neurotoxic and neuroprotective effects. Gaining an enhanced understanding of Pin1 in neuronal death may provide us with new options for the development of therapeutic target for neurodegenerative disorders.

Inhibition of Calpain Attenuates Degeneration of Substantia Nigra Neurons in the Rotenone Rat Model of Parkinson's Disease

In the central nervous system (CNS), calcium homeostasis is a critical determinant of neuronal survival. Calpain, a calcium-dependent neutral protease, is widely expressed in the brain, including substantia nigra (SN) dopaminergic (DA) neurons. Though calpain is implicated in human Parkinson's disease (PD) and corresponding animal models, the roles of specific ubiquitous calpain isoforms in PD, calpain-1 and calpain-2, remain poorly understood. In this study, we found that both isoforms are activated in a nigrostriatal pathway with increased phosphorylated synuclein following the administration of rotenone in Lewis rats, but calpain isoforms played different roles in neuronal survival. Although increased expression of calpain-1 and calpain-2 were detected in the SN of rotenone-administered rats, calpain-1 expression was not altered significantly after treatment with calpain inhibitor (calpeptin); this correlated with neuronal survival. By contrast, increased calpain-2 expression in the SN of rotenone rats correlated with neuronal death, and calpeptin treatment significantly attenuated calpain-2 and neuronal death. Calpain inhibition by calpeptin prevented glial (astroglia/microglia) activation in rotenone-treated rats in vivo, promoted M2-type microglia, and protected neurons. These data suggest that enhanced expression of calpain-1 and calpain-2 in PD models differentially affects glial activation and neuronal survival; thus, the attenuation of calpain-2 may be important in reducing SN neuronal loss in PD.

A bibliometric analysis of PIN1 and cell death

Background: Regulation of cell death plays a key role in numerous diseases. As a proline isomerase, prolyl cis-trans isomerase NIMA-interacting 1 (Pin1) is important for the regulation of signaling pathways. An in-depth understanding of how Pin1 participates in the process of cell death, which affects the occurrence and development of diseases, will aid in the discovery of new disease mechanisms and therapeutic methods. Thus, the purpose of our study was to discover the research trends and hotspots of Pin1 and cell death through bibliometric analyses and to provide insights for understanding the future development of basic research and treatment of diseases.

Methods: Documents were extracted from the Web of Science Core Collection on 7 May 2022. We selected articles and reviews published in English from 2000 to 2021, and visual and statistical analyses of countries, institutions, authors, references and keywords were performed using VOSviewer 1.6.18 and CiteSpace 5.8.

Results: A total of 395 articles and reviews were selected. Since 2001, the number of articles on Pin1 and cell death has increased annually. Publications come from 43 countries, with the US having the most publications and citations. We identified 510 authors, with Giannino Del Sal having the most articles and Paola Zacchi having the most co-citations. The Journal of Biological Chemistry is the most researched journal, and Nature and its subjournals are the most cited journals. Apoptosis, phosphorylation, and breast cancer were the three most common keywords.

Conclusion: The number of documents showed an increasing trend from 2001 to 2014. Stagnant growth after 2014 may be related to the absence of new research hotspots. Cooperative links between core institutions need to be strengthened, and the institution with the highest citation count in recent years is Fujian Medical University in China. The role of Pin1 in cell death requires further research to discover new research hotspots. Before breakthroughs in molecular mechanism or signaling pathway research, future research will focus more on the treatment of diseases represented by Pin1 inhibitors.

Diel Fluctuation Superimposed on Steady High pCO2 Generates the Most Serious Cadmium Toxicity to Marine Copepods

Coastal systems experience diel fluctuation of pCO₂ and cadmium (Cd) pollution; nevertheless, the effect of fluctuating pCO₂ on Cd biotoxicity is poorly known. In this study, we initially performed the isotopically enriched organism bioassay to label Tigriopus japonicus with ¹¹³Cd (5 μg/L) to determine the Cd accumulation rate constant (k_accu) under ambient (400 μatm) and steadily (1000 μatm) and fluctuatingly elevated (1000 ± 600 μatm) pCO₂ conditions for 48 h. Next, T. japonicus was interactively subjected to the above pCO₂ exposures at Cd (control, 5, and 500 μg/L) treatments for 7 d. Biochemical and physiological responses for copepods were analyzed. The results showed that steadily increased pCO₂ facilitated Cd bioaccumulation compared to ambient pCO₂, and it was more under fluctuating acidification conditions. Despite compensatory reactions (e.g., increased energy production), Cd ultimately induced oxidative damage and apoptosis. Meanwhile, combined treatment exhibited higher toxicity (e.g., increased apoptosis) relative to Cd exposure, and even more if fluctuating acidification was considered. Intriguingly, fluctuating acidification inhibited Cd exclusion in Cd-treated copepods compared to steady acidification, linking to higher Cd k_accu and bioaccumulation. Collectively, CO₂-driven acidification could aggravate Cd toxicity, providing a mechanistic understanding of the interaction between seawater acidification and Cd pollution in marine copepods.

Dose-Related Reduction in Hippocampal Neuronal Populations in Fetal Alcohol Exposed Vervet Monkeys

Fetal alcohol spectrum disorder (FASD) is a chronic debilitating condition resulting in behavioral and intellectual impairments and is considered the most prevalent form of preventable mental retardation in the industrialized world. We previously reported that 2-year-old offspring of vervet monkey (Chlorocebus sabeus) dams drinking, on average, 2.3 ± 0.49 g ethanol per Kg maternal body weight 4 days per week during the last third of pregnancy had significantly lower numbers of CA1 (−51.6%), CA2 (−51.2%) and CA3 (−42.8%) hippocampal neurons, as compared to age-matched sucrose controls. Fetal alcohol-exposed (FAE) offspring also showed significantly lower volumes for these structures at 2 years of age. In the present study, we examined these same parameters in 12 FAE offspring with a similar average but a larger range of ethanol exposures (1.01–2.98 g/Kg/day; total ethanol exposure 24–158 g/Kg). Design-based stereology was performed on cresyl violet-stained and doublecortin (DCX)-immunostained sections of the hippocampus. We report here significant neuronal deficits in the hippocampus with a significant negative correlation between daily dose and neuronal population in CA1 (r² = 0.486), CA2 (r² = 0.492), and CA3 (r² = 0.469). There were also significant correlations between DCX population in the dentate gyrus and daily dose (r² = 0.560). Both correlations were consistent with linear dose-response models. This study illustrates that neuroanatomical sequelae of fetal ethanol exposure are dose-responsive and suggests that there may be a threshold for this effect.

In vitro Model Systems for Studies Into Retinal Neuroprotection

Therapy development for neurodegenerative diseases of the retina constitutes a major unmet medical need, and this may be particularly relevant for inherited diseases of the retina, which are largely untreatable to this day. Therapy development necessitates appropriate models to improve the understanding of the underlying degenerative mechanisms, as well as for the testing and evaluation of novel treatment approaches. This review provides an overview of various in vitro model systems used to study retinal neuroprotection. The in vitro methods and technologies discussed range from primary retinal cell cultures and cell lines, to retinal organoids and organotypic retinal explants, to the cultivation of whole eyeballs. The advantages and disadvantages of these methods are compared and evaluated, also in view of the 3R principles (i.e., the refinement, reduction, and replacement of live animal testing), to identify suitable in vitro alternatives for in vivo experimentation. The article further expands on the use of in vitro models to test and evaluate neuroprotective treatments and to aid the development of retinal drug delivery systems. Among the pharmacological agents tested and characterized in vitro are such that interfere with aberrant cyclic guanosine monophosphate (cGMP) -signaling or such that inhibit the activities of poly (ADP-ribose) polymerase (PARP), histone deacetylases (HDAC), calpain-type proteases, as well as unfolded protein response-related stress. We then introduce nanoparticle-based drug delivery systems and discuss how different in vitro systems may be used to assess their efficacy in the treatment of retinal diseases. The summary provides a brief comparison of available in vitro models and relates their advantages and limitations to the various experimental requirements, for instance, for studies into disease mechanisms, novel treatments, or retinal toxicity. In many cases, combinations of different in vitro models may be required to obtain a comprehensive view of the efficacy of a given retinal neuroprotection approach.

Correlation of intraventricular nicardipine for refractory vasospasm in aneurysmal subarachnoid hemorrhage with improved neurophysiology on intracranial multimodality monitoring: illustrative case

BACKGROUND

Cerebral vasospasm after aneurysmal subarachnoid hemorrhage can lead to considerable mortality and morbidity affecting the intracranial vessels, leading to delayed cerebral ischemia and stroke. Therapeutic options for patients with treatment-refractory vasospasm are limited, particularly in the setting of significant cardiopulmonary disease. Administration of nicardipine, a calcium channel blocker, into the intrathecal space may represent a potential treatment option for this population.

OBSERVATIONS

A 56-year-old woman had treatment-refractory vasospasm, severe acute respiratory distress syndrome, and Takotsubo cardiomyopathy. As an adjunct to vasopressor administration and endovascular intraarterial calcium channel blocker administration, the patient received intraventricular nicardipine. The patient demonstrated improved neurophysiology on invasive multimodality neuromonitoring, with increased cerebral blood flow and oxygenation as a result of intraventricular nicardipine administration.

LESSONS

Intraventricular nicardipine can be used as rescue therapy for patients with treatment-refractory cerebral vasospasm. This case demonstrates that intrathecal nicardipine may prevent delayed ischemic neurological deficits and improve outcomes.

Inherited Retinal Degeneration: PARP-Dependent Activation of Calpain Requires CNG Channel Activity

Inherited retinal degenerations (IRDs) are a group of blinding diseases, typically involving a progressive loss of photoreceptors. The IRD pathology is often based on an accumulation of cGMP in photoreceptors and associated with the excessive activation of calpain and poly (ADP-ribose) polymerase (PARP). Inhibitors of calpain or PARP have shown promise in preventing photoreceptor cell death, yet the relationship between these enzymes remains unclear. To explore this further, organotypic retinal explant cultures derived from wild-type and IRD-mutant mice were treated with inhibitors specific for calpain, PARP, and voltage-gated Ca²⁺ channels (VGCCs). The outcomes were assessed using in situ activity assays for calpain and PARP and immunostaining for activated calpain-2, poly (ADP-ribose), and cGMP, as well as the TUNEL assay for cell death detection. The IRD models included the Pde6b-mutant rd1 mouse and rd1*Cngb1^−/− double-mutant mice, which lack the beta subunit of the rod cyclic nucleotide-gated (CNG) channel and are partially protected from rd1 degeneration. We confirmed that an inhibition of either calpain or PARP reduces photoreceptor cell death in rd1 retina. However, while the activity of calpain was decreased by the inhibition of PARP, calpain inhibition did not alter the PARP activity. A combination treatment with calpain and PARP inhibitors did not synergistically reduce cell death. In the slow degeneration of rd1*Cngb1^−/− double mutant, VGCC inhibition delayed photoreceptor cell death, while PARP inhibition did not. Our results indicate that PARP acts upstream of calpain and that both are part of the same degenerative pathway in Pde6b-dependent photoreceptor degeneration. While PARP activation may be associated with CNG channel activity, calpain activation is linked to VGCC opening. Overall, our data highlights PARP as a target for therapeutic interventions in IRD-type diseases.

Calpain Inhibitors as Potential Therapeutic Modulators in Neurodegenerative Diseases

It is considered a significant challenge to understand the neuronal cell death mechanisms with a suitable cure for neurodegenerative disorders in the coming years. Calpains are one of the best-considered "cysteine proteases activated" in brain disorders. Calpain is an important marker and mediator in the pathophysiology of neurodegeneration. Calpain activation being the essential neurodegenerative factor causing apoptotic machinery activation, it is crucial to develop reliable and effective approaches to prevent calpain-mediated apoptosis in degenerating neurons. It has been recently seen that the "inhibition of calpain activation" has appeared as a possible therapeutic target for managing neurodegenerative diseases. A systematic literature review of PubMed, Medline, Bentham, Scopus, and EMBASE (Elsevier) databases was conducted. The present article reviews the basic pathobiology and role of selective calpain inhibitors used in various neurodegenerative diseases as a therapeutic target.

Sustained Energy Deficit Following Perinatal Asphyxia: A Shift towards the Fructose-2,6-bisphosphatase (TIGAR)-Dependent Pentose Phosphate Pathway and Postnatal Development

Labor and delivery entail a complex and sequential metabolic and physiologic cascade, culminating in most circumstances in successful childbirth, although delivery can be a risky episode if oxygen supply is interrupted, resulting in perinatal asphyxia (PA). PA causes an energy failure, leading to cell dysfunction and death if re-oxygenation is not promptly restored. PA is associated with long-term effects, challenging the ability of the brain to cope with stressors occurring along with life. We review here relevant targets responsible for metabolic cascades linked to neurodevelopmental impairments, that we have identified with a model of global PA in rats. Severe PA induces a sustained effect on redox homeostasis, increasing oxidative stress, decreasing metabolic and tissue antioxidant capacity in vulnerable brain regions, which remains weeks after the insult. Catalase activity is decreased in mesencephalon and hippocampus from PA-exposed (AS), compared to control neonates (CS), in parallel with increased cleaved caspase-3 levels, associated with decreased glutathione reductase and glutathione peroxidase activity, a shift towards the TIGAR-dependent pentose phosphate pathway, and delayed calpain-dependent cell death. The brain damage continues long after the re-oxygenation period, extending for weeks after PA, affecting neurons and glial cells, including myelination in grey and white matter. The resulting vulnerability was investigated with organotypic cultures built from AS and CS rat newborns, showing that substantia nigra TH-dopamine-positive cells from AS were more vulnerable to 1 mM of H2O2 than those from CS animals. Several therapeutic strategies are discussed, including hypothermia; N-acetylcysteine; memantine; nicotinamide, and intranasally administered mesenchymal stem cell secretomes, promising clinical translation.

Targeting Programmed Cell Death to Improve Stem Cell Therapy: Implications for Treating Diabetes and Diabetes-Related Diseases

Stem cell therapies have shown promising therapeutic effects in restoring damaged tissue and promoting functional repair in a wide range of human diseases. Generations of insulin-producing cells and pancreatic progenitors from stem cells are potential therapeutic methods for treating diabetes and diabetes-related diseases. However, accumulated evidence has demonstrated that multiple types of programmed cell death (PCD) existed in stem cells post-transplantation and compromise their therapeutic efficiency, including apoptosis, autophagy, necroptosis, pyroptosis, and ferroptosis. Understanding the molecular mechanisms in PCD during stem cell transplantation and targeting cell death signaling pathways are vital to successful stem cell therapies. In this review, we highlight the research advances in PCD mechanisms that guide the development of multiple strategies to prevent the loss of stem cells and discuss promising implications for improving stem cell therapy in diabetes and diabetes-related diseases.

CO2-driven seawater acidification increases cadmium toxicity in a marine copepod

Here, we examined the 48-h acute toxicity of cadmium (Cd) in the marine copepod Tigriopus japonicus under two pCO₂ concentrations (400 and 1000 μatm). Subsequently, T. japonicus was interactively exposed to different pCO₂ (400, 1000 μatm) and Cd (control, 500 μg/L) treatments for 48 h. After exposure, biochemical and physiological responses were analyzed for the copepods. The results showed that the 48-h LC₅₀ values of Cd were calculated as 12.03 mg/L and 9.08 mg/L in T. japonicus, respectively, under 400 and 1000 μatm pCO₂ conditions. Cd exposure significantly promoted Cd exclusion/glycolysis, detoxification/stress response, and oxidative stress/apoptosis while it depressed that of antioxidant capacity. Intriguingly, CO₂-driven acidification enhanced Cd bioaccumulation and its toxicity in T. japonicus. Overall, our study provides a mechanistic understanding about the interaction between seawater acidification and Cd pollution in marine copepods.

Remyelination in PNS and CNS: current and upcoming cellular and molecular strategies to treat disabling neuropathies

Myelin is a lipid-rich nerve cover that consists of glial cell's plasmalemma layers and accelerates signal conduction. Axon-myelin contact is a source for many developmental and regenerative signals of myelination. Intra- or extracellular factors including both enhancers and inhibitors are other factors affecting the myelination process. Myelin damages are observed in several congenital and hereditary diseases, physicochemical conditions, infections, or traumatic insults, and remyelination is known as an intrinsic response to injuries. Here we discuss some molecular events and conditions involved in de- and remyelination and compare the phenomena of remyelination in CNS and PNS. We have explained applying some of these molecular events in myelin restoration. Finally, the current and upcoming treatment strategies for myelin restoration are explained in three groups of immunotherapy, endogenous regeneration enhancement, and cell therapy to give a better insight for finding the more effective rehabilitation strategies considering the underlying molecular events of a lesion formation and its current condition.

A Novel Calpain Inhibitor Compound Has Protective Effects on a Zebrafish Model of Spinocerebellar Ataxia Type 3

Spinocerebellar ataxia type 3 (SCA3) is a hereditary ataxia caused by inheritance of a mutated form of the human ATXN3 gene containing an expanded CAG repeat region, encoding a human ataxin-3 protein with a long polyglutamine (polyQ) repeat region. Previous studies have demonstrated that ataxin-3 containing a long polyQ length is highly aggregation prone. Cleavage of the ataxin-3 protein by calpain proteases has been demonstrated to be enhanced in SCA3 models, leading to an increase in the aggregation propensity of the protein. Here, we tested the therapeutic potential of a novel calpain inhibitor BLD-2736 for the treatment of SCA3 by testing its efficacy on a transgenic zebrafish model of SCA3. We found that treatment with BLD-2736 from 1 to 6 days post-fertilisation (dpf) improves the swimming of SCA3 zebrafish larvae and decreases the presence of insoluble protein aggregates. Furthermore, delaying the commencement of treatment with BLD-2736, until a timepoint when protein aggregates were already known to be present in the zebrafish larvae, was still successful at removing enhanced green fluorescent protein (EGFP) fused-ataxin-3 aggregates and improving the zebrafish swimming. Finally, we demonstrate that treatment with BLD-2736 increased the synthesis of LC3II, increasing the activity of the autophagy protein quality control pathway. Together, these findings suggest that BLD-2736 warrants further investigation as a treatment for SCA3 and related neurodegenerative diseases.

Thioredoxin-1 regulates calcium homeostasis in MPP+ /MPTP-induced Parkinson's disease models

Disturbance in calcium (Ca²⁺ ) homeostasis has been involved in a variety of neuropathological conditions including Parkinson's disease (PD). The Ca²⁺ channel, transient receptor potential channel 1 (TRPC1), plays a protective role in regulating entry of Ca²⁺ activated by store depletion of Ca²⁺ in endoplasmic reticulum (ER). We have showed that thioredoxin-1 (Trx-1) plays a role in suppressing ER stress in PD. However, whether Trx-1 regulates TRPC1 expression in PD is still unknown. In the present study, we demonstrated that treatment of 1-methyl-4-phenylpyridinum ion (MPP⁺ ) significantly reduced the expression of TRPC1 in PC12 cells, which was restored by Trx-1 overexpression, and further decreased significantly by Trx-1 siRNA. Moreover, we found that Ca²⁺ entered into the cells was decreased by MPP⁺ in PC 12 cells, which was restored by Trx-1 overexpression, and further decreased by Trx-1 siRNA. MPP⁺ significantly increased calcium-dependent cysteine protease calpain1 expression in PC12 cells, which was suppressed by Trx-1 overexpression. Calpain1 expression was increased by Trx-1 siRNA or SKF96365, an inhibitor of TRPC1. Moreover, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) decreased TRPC1 expression in the substantia nigra pars compacta region (SNpc), which was restored in mice overexpressing Trx-1, and further decreased in mice of knockdown Trx-1. Inversely, the expression of calpain1 was increased by MPTP, which was suppressed in mice overexpressing Trx-1, and further increased in mice of knockdown Trx-1. In conclusion, Trx-1 regulates the Ca²⁺ entry through regulating TRPC1 expression after treatment of MPP⁺ /MPTP.

Transcriptome analysis of liver elucidates key immune-related pathways in Nile tilapia Oreochromis niloticus following infection with tilapia lake virus

Nile tilapia (Oreochromis niloticus) is one of the most important aquaculture species farmed worldwide. However, the recent emergence of tilapia lake virus (TiLV) disease, also known as syncytial hepatitis of tilapia, has threatened the global tilapia industry. To gain more insight regarding the host response against the disease, the transcriptional profiles of liver in experimentally-infected and control tilapia were compared. Analysis of RNA-Seq data identified 4640 differentially expressed genes (DEGs), which were involved among others in antigen processing and presentation, MAPK, apoptosis, necroptosis, chemokine signaling, interferon, NF-kB, acute phase response and JAK-STAT pathways. Enhanced expression of most of the DEGs in the above pathways suggests an attempt by tilapia to resist TiLV infection. However, upregulation of some of the key genes such as BCL2L1 in apoptosis pathway; NFKBIA in NF-kB pathway; TRFC in acute phase response; and SOCS, EPOR, PI3K and AKT in JAK-STAT pathway and downregulation of the genes, namely MAP3K7 in MAPK pathway; IFIT1 in interferon; and TRIM25 in NF-kB pathway suggested that TiLV was able to subvert the host immune response to successfully establish the infection. The study offers novel insights into the cellular functions that are affected following TiLV infection and will serve as a valuable genomic resource towards our understanding of susceptibility of tilapia to TiLV infection.

Inhibition of extracellular signal-regulated kinase/calpain-2 pathway reduces neuroinflammation and necroptosis after cerebral ischemia-reperfusion injury in a rat model of cardiac arrest

BACKGROUND

Cerebral ischemia-reperfusion injury (CIRI) is the leading cause of poor neurological prognosis after cardiopulmonary resuscitation (CPR). We previously reported that the extracellular signal-regulated kinase (ERK) activation mediates CIRI. Here, we explored the potential ERK/calpain-2 pathway role in CIRI using a rat model of cardiac arrest (CA).

METHODS

Adult male Sprague-Dawley rats suffered from CA/CPR-induced CIRI, received saline, DMSO, PD98059 (ERK1/2 inhibitor, 0.3 mg/kg), or MDL28170 (calpain inhibitor, 3.0 mg/kg) after spontaneous circulation recovery. The survival rate and the neurological deficit score (NDS) were utilized to assess the brain function. Hematoxylin stain, Nissl staining, and transmission electron microscopy were used to evaluate the neuron injury. The expression levels of p-ERK, ERK, calpain-2, neuroinflammation-related markers (GFAP, Iba1, IL-1β, TNF-α), and necroptosis proteins (TNFR1, RIPK1, RIPK3, p-MLKL, and MLKL) in the brain tissues were determined by western blotting and immunohistochemistry. Fluorescent multiplex immunohistochemistry was used to analyze the p-ERK, calpain-2, and RIPK3 co-expression in neurons, and RIPK3 expression levels in microglia or astrocytes.

RESULTS

At 24 h after CA/CPR, the rats in the saline-treated and DMSO groups presented with injury tissue morphology, low NDS, ERK/calpain-2 pathway activation, and inflammatory cytokine and necroptosis protein over-expression in the brain tissue. After PD98059 and MDL28170 treatment, the brain function was improved, while inflammatory response and necroptosis were suppressed by ERK/calpain-2 pathway inhibition.

CONCLUSION

Inflammation activation and necroptosis involved in CA/CPR-induced CIRI were regulated by the ERK/calpain-2 signaling pathway. Inhibition of that pathway can reduce neuroinflammation and necroptosis after CIRI in the CA model rats.

Age-dependent ataxia and neurodegeneration caused by an αII spectrin mutation with impaired regulation of its calpain sensitivity

The neuronal membrane-associated periodic spectrin skeleton (MPS) contributes to neuronal development, remodeling, and organization. Post-translational modifications impinge on spectrin, the major component of the MPS, but their role remains poorly understood. One modification targeting spectrin is cleavage by calpains, a family of calcium-activated proteases. Spectrin cleavage is regulated by activated calpain, but also by the calcium-dependent binding of calmodulin (CaM) to spectrin. The physiologic significance of this balance between calpain activation and substrate-level regulation of spectrin cleavage is unknown. We report a strain of C57BL/6J mice harboring a single αII spectrin point mutation (Sptan1 c.3293G > A:p.R1098Q) with reduced CaM affinity and intrinsically enhanced sensitivity to calpain proteolysis. Homozygotes are embryonic lethal. Newborn heterozygotes of either gender appear normal, but soon develop a progressive ataxia characterized biochemically by accelerated calpain-mediated spectrin cleavage and morphologically by disruption of axonal and dendritic integrity and global neurodegeneration. Molecular modeling predicts unconstrained exposure of the mutant spectrin's calpain-cleavage site. These results reveal the critical importance of substrate-level regulation of spectrin cleavage for the maintenance of neuronal integrity. Given that excessive activation of calpain proteases is a common feature of neurodegenerative disease and traumatic encephalopathy, we propose that damage to the spectrin MPS may contribute to the neuropathology of many disorders.

Guidelines for Regulated Cell Death Assays: A Systematic Summary, A Categorical Comparison, A Prospective

Over the past few years, the field of regulated cell death continues to expand and novel mechanisms that orchestrate multiple regulated cell death pathways are being unveiled. Meanwhile, researchers are focused on targeting these regulated pathways which are closely associated with various diseases for diagnosis, treatment, and prognosis. However, the complexity of the mechanisms and the difficulties of distinguishing among various regulated types of cell death make it harder to carry out the work and delay its progression. Here, we provide a systematic guideline for the fundamental detection and distinction of the major regulated cell death pathways following morphological, biochemical, and functional perspectives. Moreover, a comprehensive evaluation of different assay methods is critically reviewed, helping researchers to make a reliable selection from among the cell death assays. Also, we highlight the recent events that have demonstrated some novel regulated cell death processes, including newly reported biomarkers (e.g., non-coding RNA, exosomes, and proteins) and detection techniques.

Phenanthroline impairs βAPP processing and expression, increases p53 protein levels and induces cell cycle arrest in human neuroblastoma cells

Mis-functional βAPP processing is deemed to be the major phenomenon resulting in increased neuronal cell death, impaired neurogenesis and the loss of synapses, which eventually manifest as the complex symptoms of Alzheimer's disease. Despite of several milestones having been achieved in the field of drug development, the stigma of the disorder as an incurable disease still remains. Some ADAM proteases mediate the physiological non-amyloidogenic α-secretase processing of βAPP that generates neuroprotective sAPPα production. Earlier studies have also pointed out the role of p53 in Alzheimer's disease neuropathology, although a direct link with metalloprotease activities remains to be established. In this study, we explored the consequences of α-secretase inhibition on p53 status in cultured human neuroblastoma SH-SY5Y cells by means of specific inhibitors of ADAM10 and ADAM17 and the metal chelator and general metalloprotease inhibitor phenanthroline. We establish that, beyond the ability of all inhibitors to affect sAPPα production to varying degrees, phenanthroline specifically and dose-dependently lessened βAPP expression, a phenomenon that correlated with a strong increase in p53 protein levels and a concomitant decrease of the p53-degrading calpain protease. Furthermore, treatment of cells at concentrations of phenanthroline similar to those inducing increased levels of p53 induced cell cycle arrest leading to apoptosis. Altogether, our results identify new roles of phenanthroline in perturbing βAPP, p53 and calpain biology, and suggest that the use of this compound and its derivatives as antimicrobial and anti-cancer therapies might trigger Alzheimer's disease pathogenesis.

Involvement of the miR-137-3p/CAPN-2 Interaction in Ischemia-Reperfusion-Induced Neuronal Apoptosis through Modulation of p35 Cleavage and Subsequent Caspase-8 Overactivation

Background

Neuron survival after ischemia-reperfusion (IR) injury is the primary determinant of motor function prognosis. MicroRNA- (miR-) based gene therapy has gained attention recently. Our previous work explored the mechanisms by which miR-137-3p modulates neuronal apoptosis in both in vivo and in vitro IR models.

Methods

IR-induced motor dysfunction and spinal calpain (CAPN) subtype expression and subcellular localization were detected within 12 h post IR. Dysregulated miRs, including miR-137-3p, were identified by miR microarray analysis and confirmed by PCR. A luciferase assay confirmed CAPN-2 as a corresponding target of miR-137-3p, and their modulation of motor function was evaluated by intrathecal injection with synthetic miRs. CAPN-2 activity was measured by the intracellular Ca²⁺ concentration and mean fluorescence intensity in vitro. Neuronal apoptosis was detected by flow cytometry and TUNEL assay. The activities of p35, p25, Cdk5, and caspase-8 were evaluated by ELISA and Western blot after transfection with specific inhibitors and miRs.

Results

The IR-induced motor dysfunction time course was closely associated with upregulated expression of the CAPN-2 protein, which was mainly localized in neurons. The miR-137-3p/CAPN-2 interaction was confirmed by luciferase assay. The miR-137-3p mimic significantly improved IR-induced motor dysfunction and decreased CAPN-2 expression, even in combination with recombinant rat calpain-2 (rr-CALP2) injection, whereas the miR-137-3p inhibitor reversed these effects. Similar changes in the intracellular Ca²⁺ concentration, CAPN-2 expression, and CAPN-2 activity were observed when cells were exposed to oxygen-glucose deprivation and reperfusion (OGD/R) and transfected with synthetic miRs in vitro. Moreover, double fluorescence revealed identical neuronal localization of CAPN-2, p35, p25, and caspase-8. The decrease in CAPN-2 expression and activity was accompanied by the opposite changes in p35 activity and protein expression in cells transfected with the miR-137-3p mimic, roscovitine (a Cdk5 inhibitor), or Z-IETD-FMK (a caspase-8 inhibitor). Correspondingly, the abovementioned treatments resulted in a higher neuron survival rate than that of untreated neurons, as indicated by decreases in the apoptotic cell percentage and p25, Cdk5, caspase-8, and caspase-3 protein expression.

Conclusions

The miR-137-3p/CAPN-2 interaction modulates neuronal apoptosis during IR injury, possibly by inhibiting CAPN-2, which leads to p35 cleavage and inhibition of subsequent p25/Cdk5 and caspase-8 overactivation.

Comparative Proteomics Unveils LRRFIP1 as a New Player in the DAPK1 Interactome of Neurons Exposed to Oxygen and Glucose Deprivation

Death-associated protein kinase 1 (DAPK1) is a pleiotropic hub of a number of networked distributed intracellular processes. Among them, DAPK1 is known to interact with the excitotoxicity driver NMDA receptor (NMDAR), and in sudden pathophysiological conditions of the brain, e.g., stroke, several lines of evidence link DAPK1 with the transduction of glutamate-induced events that determine neuronal fate. In turn, DAPK1 expression and activity are known to be affected by the redox status of the cell. To delineate specific and differential neuronal DAPK1 interactors in stroke-like conditions in vitro, we exposed primary cultures of rat cortical neurons to oxygen/glucose deprivation (OGD), a condition that increases reactive oxygen species (ROS) and lipid peroxides. OGD or control samples were co-immunoprecipitated separately, trypsin-digested, and proteins in the interactome identified by high-resolution LC-MS/MS. Data were processed and curated using bioinformatics tools. OGD increased total DAPK1 protein levels, cleavage into shorter isoforms, and dephosphorylation to render the active DAPK1 form. The DAPK1 interactome comprises some 600 proteins, mostly involving binding, catalytic and structural molecular functions. OGD up-regulated 190 and down-regulated 192 candidate DAPK1-interacting proteins. Some differentially up-regulated interactors related to NMDAR were validated by WB. In addition, a novel differential DAPK1 partner, LRRFIP1, was further confirmed by reverse Co-IP. Furthermore, LRRFIP1 levels were increased by pro-oxidant conditions such as ODG or the ferroptosis inducer erastin. The present study identifies novel partners of DAPK1, such as LRRFIP1, which are suitable as targets for neuroprotection.

The role of lysosome in regulated necrosis

Lysosome is a ubiquitous acidic organelle fundamental for the turnover of unwanted cellular molecules, particles, and organelles. Currently, the pivotal role of lysosome in regulating cell death is drawing great attention. Over the past decades, we largely focused on how lysosome influences apoptosis and autophagic cell death. However, extensive studies showed that lysosome is also prerequisite for the execution of regulated necrosis (RN). Different types of RN have been uncovered, among which, necroptosis, ferroptosis, and pyroptosis are under the most intensive investigation. It becomes a hot topic nowadays to target RN as a therapeutic intervention, since it is important in many patho/physiological settings and contributing to numerous diseases. It is promising to target lysosome to control the occurrence of RN thus altering the outcomes of diseases. Therefore, we aim to give an introduction about the common factors influencing lysosomal stability and then summarize the current knowledge on the role of lysosome in the execution of RN, especially in that of necroptosis, ferroptosis, and pyroptosis.

Mechanisms of Photoreceptor Death in Retinitis Pigmentosa

Retinitis pigmentosa (RP) is the most common cause of inherited blindness and is characterised by the progressive loss of retinal photoreceptors. However, RP is a highly heterogeneous disease and, while much progress has been made in developing gene replacement and gene editing treatments for RP, it is also necessary to develop treatments that are applicable to all causative mutations. Further understanding of the mechanisms leading to photoreceptor death is essential for the development of these treatments. Recent work has therefore focused on the role of apoptotic and non-apoptotic cell death pathways in RP and the various mechanisms that trigger these pathways in degenerating photoreceptors. In particular, several recent studies have begun to elucidate the role of microglia and innate immune response in the progression of RP. Here, we discuss some of the recent progress in understanding mechanisms of rod and cone photoreceptor death in RP and summarise recent clinical trials targeting these pathways.

Synthesis of α-Ketoamide-Based Stereoselective Calpain-1 Inhibitors as Neuroprotective Agents

Calpain inhibitors have been proposed as drug candidates for neurodegenerative disorders, with ABT-957 entering clinical trials for Alzheimer's disease and mild cognitive impairment. The structure of ABT-957 was very recently disclosed, and trials were terminated owing to inadequate CNS concentrations to obtain a pharmacodynamic effect. The multistep synthesis of an α-ketoamide peptidomimetic inhibitor series potentially including ABT-957 was optimized to yield diastereomerically pure compounds that are potent and selective for calpain-1 over papain and cathepsins B and K. As the final oxidation step, with its optimized synthesis protocol, does not alter the configuration of the substrate, the synthesis of the diastereomeric pair (R)-1-benzyl-N-((S)-4-((4-fluorobenzyl)amino)-3,4-dioxo-1-phenylbutan-2-yl)-5-oxopyrrolidine-2-carboxamide (1 c) and (R)-1-benzyl-N-((R)-4-((4-fluorobenzyl)amino)-3,4-dioxo-1-phenylbutan-2-yl)-5-oxopyrrolidine-2-carboxamide (1 g) was feasible. This allowed the exploration of stereoselective inhibition of calpain-1, with 1 c (IC₅₀ =78 nM) being significantly more potent than 1 g. Moreover, inhibitor 1 c restored cognitive function in amnestic mice.

Memory and Learning Deficits Are Associated With Ca2+ Dyshomeostasis in Normal Aging

Neuronal intracellular Ca2+ homeostasis is critical to the normal physiological functions of neurons and neuronal Ca2+ dyshomeostasis has been associated with the age-related decline of cognitive functions. Accumulated evidence indicates that the underlying mechanism for this is that abnormal intracellular Ca2+ levels stimulate the dysregulation of intracellular signaling, which subsequently induces neuronal cell death. We examined intracellular Ca2+ homeostasis in cortical (in vivo) and hippocampal (in vitro) neurons from young (3-months), middle-age (12-months), and aged (24-months) wild type C57BL6J mice. We found a progressive age-related elevation of intracellular resting calcium ([Ca2+]r) in cortical (in vivo) and hippocampal (in vitro) neurons associated with increased hippocampal neuronal calpain activity and reduced cell viability. In vitro, removal of extracellular Ca2+ or treatment with SAR7334 or dantrolene reduced [Ca2+]r in all age groups and dantrolene treatment lowered calpain activity and increased cell viability. In vivo, both middle-aged and aged mice showed cognitive deficits compared to young mice, which improved after dantrolene treatment. These findings support the hypothesis that intracellular Ca2+ dyshomeostasis is a major mechanism underlying the cognitive deficits seen in both normal aging and degenerative neurologic diseases.

Calpain-2 plays a pivotal role in the inhibitory effects of propofol against TNF-α-induced autophagy in mouse hippocampal neurons

Calpains are calcium‐dependent proteases and play critical roles in neuronal autophagy induced by inflammation. Propofol has been reported to exert anti‐inflammatory effects in neurons. We aimed to identify whether and how propofol‐modulated calpain activity and neuron autophagy in response to tumour necrosis factor‐α (TNF‐α). Mouse hippocampal neurons were pre‐treated with propofol and exposed to TNF‐α. Autophagy was evaluated by fluorescent autophagy assay and by measuring LC3I and LC3II expression. Intracellular calcium concentration was measured by fluorescent assay. Calpain activation was measured by calpain activity assay. The protein expression of intracellular signalling molecules was detected by Western blot analysis. Compared with untreated control neurons, 40 ng/mL TNF‐α treatment for 2 hours induced neuron autophagy, which was attenuated by 25 μmol/L propofol. TNF‐α induced intracellular calcium accumulation, the phosphorylation of calcium/calmodulin‐dependent protein kinase II (CAMK II) and calpain‐2, calpain activation and lysosomal cathepsin B release as well as tyrosine kinase receptor B (TrkB) truncation. These effects were alleviated by propofol, calcium chelator, CAMK II inhibitor, calpain‐2 inhibitor, calpain‐2 siRNA transfection and N‐Methyl‐d‐aspartic acid (NMDA) receptor antagonist. Propofol, via NMDA receptor, inhibited TNF‐α‐mediated hippocampal neuron autophagy. The mechanism may involve calcium and calcium‐dependent signalling pathway, especially CAMK II and calpain‐2.

RSK3 mediates necroptosis by regulating phosphorylation of RIP3 in rat retinal ganglion cells

Receptor-interacting protein 3 (RIP3) plays an important role in the necroptosis signaling pathway. Our previous studies have shown that the RIP3/mixed lineage kinase domain-like protein (MLKL)-mediated necroptosis occurs in retinal ganglion cell line 5 (RGC-5) following oxygen-glucose deprivation (OGD). However, upstream regulatory pathways of RIP3 are yet to be uncovered. The purpose of the present study was to investigate the role of p90 ribosomal protein S6 kinase 3 (RSK3) in the phosphorylation of RIP3 in RGC-5 cell necroptosis following OGD. Our results showed that expression of RSK3, RIP3, and MLKL was upregulated in necroptosis of RGC-5 after OGD. A computer simulation based on our preliminary results indicated that RSK3 might interact with RIP3, which was subsequently confirmed by co-immunoprecipitation. Further, we found that the application of a specific RSK inhibitor, LJH685, or rsk3 small interfering RNA (siRNA), downregulated the phosphorylation of RIP3. However, the overexpression of rip3 did not affect the expression of RSK3, thereby indicating that RSK3 could be a possible upstream regulator of RIP3 phosphorylation in OGD-induced necroptosis of RGC-5 cells. Moreover, our in vivo results showed that pretreatment with LJH685 before acute high intraocular pressure episodes could reduce the necroptosis of retinal neurons and improve recovery of impaired visual function. Taken together, our findings suggested that RSK3 might work as an upstream regulator of RIP3 phosphorylation during RGC-5 necroptosis.

MicroRNA Alteration in Developing Rat Oligodendrocyte Precursor Cells Induced by Hypoxia-Ischemia

microRNAs (miRNAs) are involved in the pathogenesis of white matter injury (WMI). However, their roles in developing rat brains under hypoxia-ischemia (HI) insult remain unknown. Here, we examined the expression profiles of miRNAs in oligodendrocyte precursor cells using microarray analysis. We identified 162 miRNAs and only 6 were differentially regulated in HI compared with sham. Next, we used these 6 miRNAs and 525 extensively changed coding genes (fold change absolute: FC(abs) ≥2, p < 0.05) to establish the coexpression network, the result revealed that only 3 miRNAs (miR-142-3p, miR-466b-5p, and miR-146a-5p) have differentially expressed targeted mRNAs. RT-PCR analysis showed that the expression of the miRNAs was consistent with the microarray analysis. Further gene ontology and KEGG pathway analysis of the targets of these 3 miRNAs indicated that they were largely associated with neural activity. Furthermore, we found that 2 of the 3 miRNAs, miR-142-3p, and miR-466b-5p, have the same target gene, Capn6, an antiapoptotic gene that is tightly regulated in the pathogenesis of neurological diseases. Collectively, we have shown that a number of miRNAs change in oligodendrocyte precursor cells in response to HI insult in developing brains, and miR-142-3p/miR-466b-5p/Capn6 pathway might affect the pathogenesis of WMI, providing us new clues for the diagnosis and therapy for WMI.

Calpastatin peptide attenuates early brain injury following experimental subarachnoid hemorrhage

Calpain activation may have an important role in early brain injury (EBI) following subarachnoid hemorrhage (SAH). The present study investigated the effects of the calpastatin peptide, a cell-permeable peptide that functions as a potent inhibitor of calpain, on EBI in a rat SAH model. It was revealed that calpastatin peptide treatment significantly reduced SAH-induced body weight loss and neurological deficit at 72 h when compared with untreated SAH controls. Furthermore, the quantification of brain water content and the extravasation of Evans blue dye revealed a significant reduction in SAH-induced brain edema and blood-brain barrier permeability at 72 h due to treatment with the calpastatin peptide when compared with untreated SAH controls. Finally, calpastatin peptide treatment significantly attenuated the protein levels of Bax, cytochrome c, cleaved caspase-9 and cleaved caspase-3, and reduced the number of terminal deoxynucleotidyl transferase dUTP nick end labelling-positive cells in the basal cortex at 72 h after SAH when compared with untreated SAH controls. These results indicated that the calpastatin peptide may ameliorate EBI following SAH in rat models.

A multi-faceted genotoxic network of alpha-synuclein in the nucleus and mitochondria of dopaminergic neurons in Parkinson's disease: Emerging concepts and challenges

α-Synuclein is a hallmark amyloidogenic protein component of the Lewy bodies (LBs) present in dopaminergic neurons affected by Parkinson's disease (PD). Despite an enormous increase in emerging knowledge, the mechanism(s) of α-synuclein neurobiology and crosstalk among pathological events that are critical for PD progression remains enigmatic, creating a roadblock for effective intervention strategies. One confounding question is about the potential link between α-synuclein toxicity and genome instability in PD. We previously reported that pro-oxidant metal ions, together with reactive oxygen species (ROS), act as a "double whammy" in dopaminergic neurons by not only inducing genome damage but also inhibiting their repair. Our recent studies identified a direct role for chromatin-bound, oxidized α-synuclein in the induction of DNA strand breaks, which raised the question of a paradoxical role for α-synuclein's DNA binding in neuroprotection versus neurotoxicity. Furthermore, recent advances in our understanding of α-synuclein mediated mitochondrial dysfunction warrants revisiting the topics of α-synuclein pathophysiology in order to devise and assess the efficacy of α-synuclein-targeted interventions. In this review article, we discuss the multi-faceted neurotoxic role of α-synuclein in the nucleus and mitochondria with a particular emphasis on the role of α-synuclein in DNA damage/repair defects. We utilized a protein-DNA binding simulation to identify potential residues in α-synuclein that could mediate its binding to DNA and may be critical for its genotoxic functions. These emerging insights and paradigms may guide new drug targets and therapeutic modalities.

Structural Insights into the Unique Activation Mechanisms of a Non-classical Calpain and Its Disease-Causing Variants

Increased calpain activity is linked to neuroinflammation including a heritable retinal disease caused by hyper-activating mutations in the calcium-activated calpain-5 (CAPN5) protease. Although structures for classical calpains are known, the structure of CAPN5, a non-classical calpain, remains undetermined. Here we report the 2.8 Å crystal structure of the human CAPN5 protease core (CAPN5-PC). Compared to classical calpains, CAPN5-PC requires high calcium concentrations for maximal activity. Structure-based phylogenetic analysis and multiple sequence alignment reveal that CAPN5-PC contains three elongated flexible loops compared to its classical counterparts. The presence of a disease-causing mutation (c.799G>A, p.Gly267Ser) on the unique PC2L2 loop reveals a function in this region for regulating enzymatic activity. This mechanism could be transferred to distant calpains, using synthetic calpain hybrids, suggesting an evolutionary mechanism for fine-tuning calpain function by modifying flexible loops. Further, the open (inactive) conformation of CAPN5-PC provides structural insight into CAPN5-specific residues that can guide inhibitor design.