Pin1 Is Regulated by CaMKII Activation in Glutamate-Induced Retinal Neuronal Regulated Necrosis

p38 MAPK inhibitor SB202190 suppresses ferroptosis in the glutamate-induced retinal excitotoxicity glaucoma model

JOURNAL/nrgr/04.03/01300535-202410000-00031/figure1/v/2024-02-06T055622Z/r/image-tiff Glutamate excitotoxicity has been shown to play an important role in glaucoma, and glutamate can induce ferroptosis. The p38 mitogen-activated protein kinase (MAPK) pathway inhibitor SB202190 has a potential ability to suppress ferroptosis, and its downstream targets, such as p53, have been shown to be associated with ferroptosis. However, whether ferroptosis also occurs in retinal ganglion cells in response to glutamate excitotoxicity and whether inhibition of ferroptosis reduces the loss of retinal ganglion cells induced by glutamate excitotoxicity remain unclear. This study investigated ferroptosis in a glutamate-induced glaucoma rat model and explored the effects and molecular mechanisms of SB202190 on retinal ganglion cells. A glutamate-induced excitotoxicity model in R28 cells and an N-methyl-D-aspartate-induced glaucoma model in rats were used. In vitro experiments showed that glutamate induced the accumulation of iron and lipid peroxide and morphological changes of mitochondria in R28 cells, and SB202190 inhibited these changes. Glutamate induced the levels of p-p38 MAPK/p38 MAPK and SAT1 and decreased the expression levels of ferritin light chain, SLC7A11, and GPX4. SB202190 inhibited the expression of iron death-related proteins induced by glutamate. In vivo experiments showed that SB202190 attenuated N-methyl-D-aspartate-induced damage to rat retinal ganglion cells and improved visual function. These results suggest that SB202190 can inhibit ferroptosis and protect retinal ganglion cells by regulating ferritin light chain, SAT1, and SLC7A11/Gpx4 pathways and may represent a potential retina protectant.

Unveiling the role of CaMKII in retinal degeneration: from biological mechanism to therapeutic strategies

Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a family of broad substrate specificity serine (Ser)/threonine (Thr) protein kinases that play a crucial role in the Ca2+-dependent signaling pathways. Its significance as an intracellular Ca2+ sensor has garnered abundant research interest in the domain of neurodegeneration. Accumulating evidences suggest that CaMKII is implicated in the pathology of degenerative retinopathies such as diabetic retinopathy (DR), age-related macular degeneration (AMD), retinitis pigmentosa (RP) and glaucoma optic neuropathy. CaMKII can induce the aberrant proliferation of retinal blood vessels, influence the synaptic signaling, and exert dual effects on the survival of retinal ganglion cells and pigment epithelial cells. Researchers have put forth multiple therapeutic agents, encompassing small molecules, peptides, and nucleotides that possess the capability to modulate CaMKII activity. Due to its broad range isoforms and splice variants therapeutic strategies seek to inhibit specifically the CaMKII are confronted with considerable challenges. Therefore, it becomes crucial to discern the detrimental and advantageous aspects of CaMKII, thereby facilitating the development of efficacious treatment. In this review, we summarize recent research findings on the cellular and molecular biology of CaMKII, with special emphasis on its metabolic and regulatory mechanisms. We delve into the involvement of CaMKII in the retinal signal transduction pathways and discuss the correlation between CaMKII and calcium overload. Furthermore, we elaborate the therapeutic trials targeting CaMKII, and introduce recent developments in the zone of CaMKII inhibitors. These findings would enrich our knowledge of CaMKII, and shed light on the development of a therapeutic target for degenerative retinopathy.

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.

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.

Role of CAST-Drp1 Pathway in Retinal Neuron-Regulated Necrosis in Experimental Glaucoma

OBJECTIVE

Numerous studies have indicated that excitatory amino acid toxicity, such as glutamate toxicity, is involved in glaucoma. In addition, excessive glutamate can lead to an intracellular calcium overload, resulting in regulated necrosis. Our previous studies have found that the calpastatin (CAST)-calpain pathway plays an important role in retinal neuron-regulated necrosis after glutamate injury. Although inhibition of the calpain pathway can decrease regulated necrosis, necrotic cells remain. It has been suggested that there are other molecules that participate in retinal neuron-regulated necrosis. CAST is an important regulator of dynamin-related protein 1 (Drp1)-mediated mitochondrial defects. Thus, the aim of this study was to determine whether the CAST-Drp1 pathway may be an underlying signaling axis in neuron-regulated necrosis.

METHODS

Using cultured retinal neurons and in an in-vivo glaucoma model induced by glutamate overload, members of the CAST-Drp1 pathway were assessed by immunofluorescence, Western blotting, Phos-tagTM SDS-PAGE, and co-immunoprecipitation assays. Moreover, the black and white box test was performed on the rats.

RESULTS

We found that more retinal neuron-regulated necrosis and Drp1 activation as well as lower CAST levels were present in the glutamate-induced glaucoma model. Rats with glutamate-induced glaucoma exhibited impaired visual function. We also observed retinal neuron-regulated necrosis and Drp1 activity decreased, and impaired vision recovered after CAST active peptide application, indicating that the CAST-Drp1 pathway plays a critical role in retinal neuron-regulated necrosis and visual function.

CONCLUSION

The results of this study indicate that the CAST-Drp1 pathway protects against retinal neuron-regulated necrosis, which may expand the therapeutic targets for the treatment of neurodegenerative disorders involving dysfunction of glutamate metabolism, such as glaucoma.

Targeting Necroptosis: A Novel Therapeutic Option for Retinal Degenerative Diseases

The discovery of the necroptosis, a form of regulated necrosis that is mediated by receptor-interacting protein kinase 1 (RIPK1), RIPK3, and mixed-lineage kinase domain-like pseudokinase (MLKL), represents a major breakthrough that has dramatically altered the conception of necrosis - traditionally thought of as uncontrolled cell death - in various human diseases. Retinal cell death is a leading cause of blindness and has been identified in most retinal diseases, e.g., age-related macular degeneration, glaucoma, retinal detachment, retinitis pigmentosa, etc. Increasing evidence demonstrates that retinal degenerative diseases also share a common mechanism in necroptosis. Exacerbated necroptotic cell death hinders the treatment for retinal degenerative diseases. In this review, we highlight recent advances in identifying retinal necroptosis, summarize the underlying mechanisms of necroptosis in retinal degenerative diseases, and discuss potential anti-necroptosis strategies, such as selective inhibitors and chemical agents, for treating retinal degenerative diseases.

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.

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.

Role of Ca2+/Calmodulin-Dependent Protein Kinase Type II in Mediating Function and Dysfunction at Glutamatergic Synapses

Glutamatergic synapses harbor abundant amounts of the multifunctional Ca²⁺/calmodulin-dependent protein kinase type II (CaMKII). Both in the postsynaptic density as well as in the cytosolic compartment of postsynaptic terminals, CaMKII plays major roles. In addition to its Ca²⁺-stimulated kinase activity, it can also bind to a variety of membrane proteins at the synapse and thus exert spatially restricted activity. The abundance of CaMKII in glutamatergic synapse is akin to scaffolding proteins although its prominent function still appears to be that of a kinase. The multimeric structure of CaMKII also confers several functional capabilities on the enzyme. The versatility of the enzyme has prompted hypotheses proposing several roles for the enzyme such as Ca²⁺ signal transduction, memory molecule function and scaffolding. The article will review the multiple roles played by CaMKII in glutamatergic synapses and how they are affected in disease conditions.

The Pin1-CaMKII-AMPA Receptor Axis Regulates Epileptic Susceptibility

Pin1 is a unique isomerase that regulates protein conformation and function after phosphorylation. Pin1 aberration contributes to some neurological diseases, notably Alzheimer's disease, but its role in epilepsy is not fully understood. We found that Pin1-deficient mice had significantly increased seizure susceptibility in multiple chemical inducing models and developed age-dependent spontaneous epilepsy. Electrophysiologically, Pin1 ablation enhanced excitatory synaptic transmission to prefrontal cortex (PFC) pyramidal neurons without affecting their intrinsic excitability. Biochemically, Pin1 ablation upregulated AMPA receptors and GluA1 phosphorylation by acting on phosphorylated CaMKII. Clinically, Pin1 was decreased significantly, whereas phosphorylated CaMKII and GluA1 were increased in the neocortex of patients with epilepsy. Moreover, Pin1 expression restoration in the PFC of Pin1-deficient mice using viral gene transfer significantly reduced phosphorylated CaMKII and GluA1 and effectively suppressed their seizure susceptibility. Thus, Pin1-CaMKII-AMPA receptors are a novel axis controlling epileptic susceptibility, highlighting attractive new therapeutic strategies.

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.

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.

RIP3/MLKL-mediated neuronal necroptosis induced by methamphetamine at 39°C

Methamphetamine is one of the most prevalent drugs abused in the world. Methamphetamine abusers usually present with hyperpyrexia (39°C), hallucination and other psychiatric symptoms. However, the detailed mechanism underlying its neurotoxic action remains elusive. This study investigated the effects of methamphetamine + 39°C on primary cortical neurons from the cortex of embryonic Sprague-Dawley rats. Primary cortex neurons were exposed to 1 mM methamphetamine + 39°C. Propidium iodide staining and lactate dehydrogenase release detection showed that methamphetamine + 39°C triggered obvious necrosis-like death in cultured primary cortical neurons, which could be partially inhibited by receptor-interacting protein-1 (RIP1) inhibitor Necrostatin-1 partially. Western blot assay results showed that there were increases in the expressions of receptor-interacting protein-3 (RIP3) and mixed lineage kinase domain-like protein (MLKL) in the primary cortical neurons treated with 1 mM methamphetamine + 39°C for 3 hours. After pre-treatment with RIP3 inhibitor GSK'872, propidium iodide staining and lactate dehydrogenase release detection showed that neuronal necrosis rate was significantly decreased; RIP3 and MLKL protein expression significantly decreased. Immunohistochemistry staining results also showed that the expressions of RIP3 and MLKL were up-regulated in brain specimens from humans who had died of methamphetamine abuse. Taken together, the above results suggest that methamphetamine + 39°C can induce RIP3/MLKL regulated necroptosis, thereby resulting in neurotoxicity. The study protocol was approved by the Medical Ethics Committee of the Third Xiangya Hospital of Central South University, China (approval numbers: 2017-S026 and 2017-S033) on March 7, 2017.