Neuronal cell life, death, and axonal degeneration as regulated by the BCL-2 family proteins

The RNA-binding protein EIF4A3 promotes axon development by direct control of the cytoskeleton

The exon junction complex (EJC), nucleated by EIF4A3, is indispensable for mRNA fate and function throughout eukaryotes. We discover that EIF4A3 directly controls microtubules, independent of RNA, which is critical for neural wiring. While neuronal survival in the developing mouse cerebral cortex depends upon an intact EJC, axonal tract development requires only Eif4a3. Using human cortical organoids, we show that EIF4A3 disease mutations also impair neuronal growth, highlighting conserved functions relevant for neurodevelopmental pathology. Live imaging of growing neurons shows that EIF4A3 is essential for microtubule dynamics. Employing biochemistry and competition experiments, we demonstrate that EIF4A3 directly binds to microtubules, mutually exclusive of the EJC. Finally, in vitro reconstitution assays and rescue experiments demonstrate that EIF4A3 is sufficient to promote microtubule polymerization and that EIF4A3-microtubule association is a major contributor to axon growth. This reveals a fundamental mechanism by which neurons re-utilize core gene expression machinery to directly control the cytoskeleton.

Covalent inhibition of pro-apoptotic BAX

BCL-2-associated X protein (BAX) is a promising therapeutic target for activating or restraining apoptosis in diseases of pathologic cell survival or cell death, respectively. In response to cellular stress, BAX transforms from a quiescent cytosolic monomer into a toxic oligomer that permeabilizes the mitochondria, releasing key apoptogenic factors. The mitochondrial lipid trans-2-hexadecenal (t-2-hex) sensitizes BAX activation by covalent derivatization of cysteine 126 (C126). In this study, we performed a disulfide tethering screen to discover C126-reactive molecules that modulate BAX activity. We identified covalent BAX inhibitor 1 (CBI1) as a compound that selectively derivatizes BAX at C126 and inhibits BAX activation by triggering ligands or point mutagenesis. Biochemical and structural analyses revealed that CBI1 can inhibit BAX by a dual mechanism of action: conformational constraint and competitive blockade of lipidation. These data inform a pharmacologic strategy for suppressing apoptosis in diseases of unwanted cell death by covalent targeting of BAX C126.

Rational design of small-sized peptidomimetic inhibitors disrupting protein-protein interaction

Protein-protein interactions are fundamental to nearly all biological processes. Due to their structural flexibility, peptides have emerged as promising candidates for developing inhibitors targeting large and planar PPI interfaces. However, their limited drug-like properties pose challenges. Hence, rational modifications based on peptide structures are anticipated to expedite the innovation of peptide-based therapeutics. This review comprehensively examines the design strategies for developing small-sized peptidomimetic inhibitors targeting PPI interfaces, which predominantly encompass two primary categories: peptidomimetics with abbreviated sequences and low molecular weights and peptidomimetics mimicking secondary structural conformations. We have also meticulously detailed several instances of designing and optimizing small-sized peptidomimetics targeting PPIs, including MLL1-WDR5, PD-1/PD-L1, and Bak/Bcl-xL, among others, to elucidate the potential application prospects of these design strategies. Hopefully, this review will provide valuable insights and inspiration for the future development of PPI small-sized peptidomimetic inhibitors in pharmaceutical research endeavors.

Luteolin as a potential therapeutic candidate for lung cancer: Emerging preclinical evidence

Lung cancer is a prevalent malignant tumor and a leading cause of cancer-related fatalities globally. However, current treatments all have limitations. Therefore, there is an urgent need to identify a readily available therapeutic agent to counteract lung cancer development and progression. Luteolin is a flavonoid derived from vegetables and herbs that possesses preventive and therapeutic effects on various cancers. With the goal of providing new directions for the treatment of lung cancer, we review here the recent findings on luteolin so as to provide new ideas for the development of new anti-lung cancer drugs. The search focused on studies published between January 1995 and January 2024 that explored the use of luteolin in lung cancer. A comprehensive literature search was conducted in the SCOPUS, Google Scholar, PubMed, and Web of Science databases using the keywords "luteolin" and "lung cancer." By collecting previous literature, we found that luteolin has multiple mechanisms of therapeutic effects, including promotion of apoptosis in lung cancer cells; inhibition of tumor cell proliferation, invasion and metastasis; and modulation of immune responses. In addition, it can be used as an adjuvant to radio-chemotherapy and helps to ameliorate cancer complications. This review summarizes the structure, natural sources, physicochemical properties and pharmacokinetics of luteolin, and focuses on the anti-lung cancer mechanism of luteolin, so as to provide new ideas for the development of new anti-lung cancer drugs.

Context-Specific Stress Causes Compartmentalized SARM1 Activation and Local Degeneration in Cortical Neurons

Sterile alpha and TIR motif containing 1 (SARM1) is an inducible NADase that localizes to mitochondria throughout neurons and senses metabolic changes that occur after injury. Minimal proteomic changes are observed upon either SARM1 depletion or activation, suggesting that SARM1 does not exert broad effects on neuronal protein homeostasis. However, whether SARM1 activation occurs throughout the neuron in response to injury and cell stress remains largely unknown. Using a semiautomated imaging pipeline and a custom-built deep learning scoring algorithm, we studied degeneration in both mixed-sex mouse primary cortical neurons and male human-induced pluripotent stem cell-derived cortical neurons in response to a number of different stressors. We show that SARM1 activation is differentially restricted to specific neuronal compartments depending on the stressor. Cortical neurons undergo SARM1-dependent axon degeneration after mechanical transection, and SARM1 activation is limited to the axonal compartment distal to the injury site. However, global SARM1 activation following vacor treatment causes both cell body and axon degeneration. Context-specific stressors, such as microtubule dysfunction and mitochondrial stress, induce axonal SARM1 activation leading to SARM1-dependent axon degeneration and SARM1-independent cell body death. Our data reveal that compartment-specific SARM1-mediated death signaling is dependent on the type of injury and cellular stressor.

Transplantation of dorsal root ganglia overexpressing the NaChBac sodium channel improves locomotion after complete SCI

Spinal cord injury (SCI) is a debilitating condition currently lacking treatment. Severe SCI causes the loss of most supraspinal inputs and neuronal activity caudal to the injury, which, coupled with the limited endogenous capacity for spontaneous regeneration, can lead to complete functional loss even in anatomically incomplete lesions. We hypothesized that transplantation of mature dorsal root ganglia (DRGs) genetically modified to express the NaChBac sodium channel could serve as a therapeutic option for functionally complete SCI. We found that NaChBac expression increased the intrinsic excitability of DRG neurons and promoted cell survival and neurotrophic factor secretion in vitro. Transplantation of NaChBac-expressing dissociated DRGs improved voluntary locomotion 7 weeks after injury compared to control groups. Animals transplanted with NaChBac-expressing DRGs also possessed higher tubulin-positive neuronal fiber and myelin preservation, although serotonergic descending fibers remained unaffected. We observed early preservation of the corticospinal tract 14 days after injury and transplantation, which was lost 7 weeks after injury. Nevertheless, transplantation of NaChBac-expressing DRGs increased the neuronal excitatory input by an increased number of VGLUT2 contacts immediately caudal to the injury. Our work suggests that the transplantation of NaChBac-expressing dissociated DRGs can rescue significant motor function, retaining an excitatory neuronal relay activity immediately caudal to injury.

Unlocking the Therapeutic Potential of BCL-2 Associated Protein Family: Exploring BCL-2 Inhibitors in Cancer Therapy

Apoptosis, programmed cell death pathway, is a vital physiological mechanism that ensures cellular homeostasis and overall cellular well-being. In the context of cancer, where evasion of apoptosis is a hallmark, the overexpression of anti-apoptotic proteins like Bcl2, Bcl-xL and Mcl-1 has been documented. Consequently, these proteins have emerged as promising targets for therapeutic interventions. The BCL-2 protein family is central to apoptosis and plays a significant importance in determining cellular fate serving as a critical determinant in this biological process. This review offers a comprehensive exploration of the BCL-2 protein family, emphasizing its dual nature. Specifically, certain members of this family promote cell survival (known as anti-apoptotic proteins), while others are involved in facilitating cell death (referred to as pro-apoptotic and BH3-only proteins). The potential of directly targeting these proteins is examined, particularly due to their involvement in conferring resistance to traditional cancer therapies. The effectiveness of such targeting strategies is also discussed, considering the tumor's propensity for anti-apoptotic pathways. Furthermore, the review highlights emerging research on combination therapies, where BCL-2 inhibitors are used synergistically with other treatments to enhance therapeutic outcomes. By understanding and manipulating the BCL-2 family and its associated pathways, we open doors to innovative and more effective cancer treatments, offering hope for resistant and aggressive cases.

Non-apoptotic role of EGL-1 in exopher production and neuronal health in Caenorhabditis elegans

While traditionally studied for their pro-apoptotic functions, recent research suggests BH3-only proteins also have non-apoptotic roles. Here, we find that EGL-1, the BH3-only protein in Caenorhabditis elegans, promotes the cell-autonomous production of exophers in adult neurons. Exophers are large, micron-scale vesicles that are ejected from the cell and contain cellular components such as mitochondria. EGL-1 facilitates exopher production potentially through regulation of mitochondrial dynamics. Moreover, an endogenous, low level of EGL-1 expression appears to benefit dendritic health. Our findings provide insights into the mechanistic role of BH3-only protein in mitochondrial dynamics, downstream exopher production, and ultimately neuronal health.

Focusing on mitochondria in the brain: from biology to therapeutics

Mitochondria have multiple functions such as supplying energy, regulating the redox status, and producing proteins encoded by an independent genome. They are closely related to the physiology and pathology of many organs and tissues, among which the brain is particularly prominent. The brain demands 20% of the resting metabolic rate and holds highly active mitochondrial activities. Considerable research shows that mitochondria are closely related to brain function, while mitochondrial defects induce or exacerbate pathology in the brain. In this review, we provide comprehensive research advances of mitochondrial biology involved in brain functions, as well as the mitochondria-dependent cellular events in brain physiology and pathology. Furthermore, various perspectives are explored to better identify the mitochondrial roles in neurological diseases and the neurophenotypes of mitochondrial diseases. Finally, mitochondrial therapies are discussed. Mitochondrial-targeting therapeutics are showing great potentials in the treatment of brain diseases.

Tanshinone IIA Alleviates Traumatic Brain Injury by Reducing Ischemia‒Reperfusion via the miR-124-5p/FoxO1 Axis

Background

Cerebral ischemia-reperfusion injury is a common complication of ischemic stroke that affects the prognosis of patients with ischemic stroke. The lipid-soluble diterpene Tanshinone IIA, which was isolated from Salvia miltiorrhiza, has been indicated to reduce cerebral ischemic injury. In this study, we investigated the molecular mechanism of Tanshinone IIA in alleviating reperfusion-induced brain injury.

Methods

Middle cerebral artery occlusion animal models were established, and neurological scores, tetrazolium chloride staining, brain volume quantification, wet and dry brain water content measurement, Nissl staining, enzyme-linked immunosorbent assay, flow cytometry, western blotting, and reverse transcription-quantitative polymerase chain reaction were performed. The viability of cells was measured by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide assays, while cell damage was measured by lactate dehydrogenase release in the in vitro oxygen glucose deprivation model. In addition, enzyme-linked immunosorbent assay, flow cytometry, western blotting, and reverse transcription-quantitative polymerase chain reaction were used to evaluate the therapeutic effect of Tanshinone IIA on ischemia/reperfusion (I/R) induced brain injury, as well as its effects on the inflammatory response and neuronal apoptosis, in vivo and in vitro. Furthermore, this study validated the targeting relationship between miR-124-5p and FoxO1 using a dual luciferase assay. Finally, we examined the role of Tanshinone IIA in brain injury from a molecular perspective by inhibiting miR-124-5p or increasing FoxO1 levels.

Results

After treatment with Tanshinone IIA in middle cerebral artery occlusion-reperfusion (MCAO/R) rats, the volume of cerebral infarction was reduced, the water content of the brain was decreased, the nerve function of the rats was significantly improved, and the cell damage was significantly reduced. In addition, Tanshinone IIA effectively inhibited the I/R-induced inflammatory response and neuronal apoptosis, that is, it inhibited the expression of inflammatory cytokines IL-1β, IL-6, TNF-α, decreased the expression of apoptotic protein Bax and Cleaved-caspase-3, and promoted the expression of antiapoptotic protein Bcl-2. In vitro oxygen-glucose deprivation/reoxygenation (OGD/R) cell model, Tanshinone IIA also inhibited the expression of inflammatory factors in neuronal cells and inhibited the occurrence of neuronal apoptosis. In addition, Tanshinone IIA promoted the expression of miR-124-5p. Transfection of miR-124-5p mimic has the same therapeutic effect as Tanshinone IIA and positive therapeutic effect on OGD cells, while transfection of miR-124-5p inhibitor has the opposite effect. The targeting of miR-124-5p negatively regulates FoxO1 expression. Inhibition of miR-124-5p or overexpression of FoxO1 can weaken the inhibitory effect of Tanshinone IIA on brain injury induced by I/R, while inhibition of miR-124-5p and overexpression of FoxO1 can further weaken the effect of Tanshinone IIA.

Conclusion

Tanshinone IIA alleviates ischemic-reperfusion brain injury by inhibiting neuroinflammation through the miR-124-5p/FoxO1 axis. This finding provides a theoretical basis for mechanistic research on cerebral ischemia-reperfusion injury.

Stroke in the Time of Circadian Medicine

Time-of-day significantly influences the severity and incidence of stroke. Evidence has emerged not only for circadian governance over stroke risk factors, but also for important determinants of clinical outcome. In this review, we provide a comprehensive overview of the interplay between chronobiology and cerebrovascular disease. We discuss circadian regulation of pathophysiological mechanisms underlying stroke onset or tolerance as well as in vascular dementia. This includes cell death mechanisms, metabolism, mitochondrial function, and inflammation/immunity. Furthermore, we present clinical evidence supporting the link between disrupted circadian rhythms and increased susceptibility to stroke and dementia. We propose that circadian regulation of biochemical and physiological pathways in the brain increase susceptibility to damage after stroke in sleep and attenuate treatment effectiveness during the active phase. This review underscores the importance of considering circadian biology for understanding the pathology and treatment choice for stroke and vascular dementia and speculates that considering a patient's chronotype may be an important factor in developing precision treatment following stroke.

Pharmacological Targeting of Senescence with Senolytics as a New Therapeutic Strategy for Neurodegeneration

Cellular senescence is a state of permanent cell-cycle arrest. Early in life, senescence has a physiologic role in tumor suppression and wound healing. However, gradually, as these senescent cells accumulate over the lifespan of an organism, they contribute to inflammation and the progression of age-related diseases, including neurodegeneration. Targeting senescent cells using a class of drugs known as "senolytics" holds great promise for the management of Alzheimer's and Parkinson's disease. Already, several senolytic compounds have been shown to ameliorate cognitive deficits across several preclinical models of neurodegeneration. Most of these senolytics (e.g., dasatinib) are repurposed clinical or experimental anticancer drugs, which trigger apoptosis of senescent cells by interfering with pro-survival pathways. However, outside of their senolytic function, many first-generation senolytics also have other less appreciated neuroprotective effects, such as potent antioxidant and anti-inflammatory activity. In addition, some senolytic drugs may also have negative dose-limiting toxicities, including thrombocytopenia. In this review, we discuss the various biologic pathways targeted by the leading senolytic drugs, namely dasatinib, quercetin, fisetin, and navitoclax. We further evaluate the clinical transability of these compounds for neurodegeneration, assessing their adverse effects, pharmacokinetic properties, and chemical structure. SIGNIFICANCE STATEMENT: Currently, there are no effective disease-modifying treatments for the most prevalent neurodegenerative disorders, including Alzheimer's and Parkinson's disease. Some of the drugs currently available for treating these diseases are associated with unwanted side-effects and/or become less efficacious with time. Therefore, researchers have begun to explore new innovative treatments for these belligerent diseases, including senolytic drugs. These agents lead to the apoptosis of senescent cells thereby preventing their deleterious role in neurodegeneration.

Depletion of muscularis macrophages ameliorates inflammation-driven dysmotility in murine colitis model

Previously, the presence of a blood-myenteric plexus barrier and its disruption was reported in experimentally induced colitis via a macrophage-dependent process. The aim of this study is to reveal how myenteric barrier disruption and subsequent neuronal injury affects gut motility in vivo in a murine colitis model. We induced colitis with dextran sulfate sodium (DSS), with the co-administration of liposome-encapsulated clodronate (L-clodronate) to simultaneously deplete blood monocytes contributing to macrophage infiltration in the inflamed muscularis of experimental mice. DSS-treated animals receiving concurrent L-clodronate injection showed significantly decreased blood monocyte numbers and colon muscularis macrophage (MM) density compared to DSS-treated control (DSS-vehicle). DSS-clodronate-treated mice exhibited significantly slower whole gut transit time than DSS-vehicle-treated animals and comparable to that of controls. Experiments with oral gavage-fed Evans-blue dye showed similar whole gut transit times in DSS-clodronate-treated mice as in control animals. Furthermore, qPCR-analysis and immunofluorescence on colon muscularis samples revealed that factors associated with neuroinflammation and neurodegeneration, including Bax1, Hdac4, IL-18, Casp8 and Hif1a are overexpressed after DSS-treatment, but not in the case of concurrent L-clodronate administration. Our findings highlight that MM-infiltration in the muscularis layer is responsible for colitis-associated dysmotility and enteric neuronal dysfunction along with the release of mediators associated with neurodegeneration in a murine experimental model.

Cell death classification: A new insight based on molecular mechanisms

Cells tend to disintegrate themselves or are forced to undergo such destructive processes in critical circumstances. This complex cellular function necessitates various mechanisms and molecular pathways in order to be executed. The very nature of cell death is essentially important and vital for maintaining homeostasis, thus any type of disturbing occurrence might lead to different sorts of diseases and dysfunctions. Cell death has various modalities and yet, every now and then, a new type of this elegant procedure gets to be discovered. The diversity of cell death compels the need for a universal organizing system in order to facilitate further studies, therapeutic strategies and the invention of new methods of research. Considering all that, we attempted to review most of the known cell death mechanisms and sort them all into one arranging system that operates under a simple but subtle decision-making (If \ Else) order as a sorting algorithm, in which it decides to place and sort an input data (a type of cell death) into its proper set, then a subset and finally a group of cell death. By proposing this algorithm, the authors hope it may solve the problems regarding newer and/or undiscovered types of cell death and facilitate research and therapeutic applications of cell death.

Contribution of Nischarin/IRAS in CNS development, injury and diseases

BACKGROUND

Murine Nischarin and its human homolog IRAS are scaffold proteins highly expressed in the central nervous system (CNS). Nischarin was initially discovered as a tumor suppressor protein, and recent studies have also explored its potential value in the CNS. Research on IRAS has largely focused on its effect on opioid dependence. Although the role of Nischarin/IRAS in the physiological function and pathological process of the CNS has gradually attracted attention and the related research results are expected to be applied in clinical practice, there is no systematic review of the role and mechanisms of Nischarin/IRAS in the CNS so far.

AIM OF REVIEW

This review will systematically analyze the role and mechanism of Nischarin/IRAS in the CNS, and provide necessary references and possible targets for the treatment of neurological diseases, thereby broadening the direction of Nischarin/IRAS research and facilitating clinical translation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The pathophysiological processes affected by dysregulation of Nischarin/IRAS expression in the CNS are mainly introduced, including spinal cord injury (SCI), opioid dependence, anxiety, depression, and autism. The molecular mechanisms such as factors regulating Nischarin/IRAS expression and signal transduction pathways regulated by Nischarin/IRAS are systematically summarized. Finally, the clinical application of Nischarin/IRAS has been prospected.

Mitochondrial-targeted and ROS-responsive nanocarrier via nose-to-brain pathway for ischemic stroke treatment

Oxidative stress injury and mitochondrial dysfunction are major obstacles to neurological functional recovery after ischemic stroke. The development of new approaches to simultaneously diminish oxidative stress and resist mitochondrial dysfunction is urgently needed. Inspired by the overproduced reactive oxygen species (ROS) at ischemic neuron mitochondria, multifunctional nanoparticles with ROS-responsiveness and mitochondrial-targeted (SPNPs) were engineered, achieving specific targeting delivery and controllable drug release at ischemic penumbra. Due to the nose-to-brain pathway, SPNPs which were encapsulated in a thermo-sensitive gel by intranasal administration were directly delivered to the ischemic penumbra bypassing the blood‒brain barrier (BBB) and enhancing delivery efficiency. The potential of SPNPs for ischemic stroke treatment was systematically evaluated in vitro and in rat models of middle cerebral artery occlusion (MCAO). Results demonstrated the mitochondrial-targeted and protective effects of SPNPs on H2O2-induced oxidative damage in SH-SY5Y cells. In vivo distribution analyzed by fluorescence imaging proved the rapid and enhanced active targeting of SPNPs to the ischemic area in MCAO rats. SPNPs by intranasal administration exhibited superior therapeutic efficacy by alleviating oxidative stress, diminishing inflammation, repairing mitochondrial function, and decreasing apoptosis. This strategy provided a multifunctional delivery system for the effective treatment of ischemic injury, which also implies a potential application prospect for other central nervous diseases.

Reinventing the Penumbra - the Emerging Clockwork of a Multi-modal Mechanistic Paradigm

The concept of the ischemic penumbra was originally defined as the area around a necrotic stroke core and seen as the tissue at imminent risk of further damage. Today, the penumbra is generally considered as time-sensitive hypoperfused brain tissue with decreased oxygen and glucose availability, salvageable tissue as treated by intervention, and the potential target for neuroprotection in focal stroke. The original concept entailed electrical failure and potassium release but one short of neuronal cell death and was based on experimental stroke models, later confirmed in clinical imaging studies. However, even though the basic mechanisms have translated well, conferring brain protection, and improving neurological outcome after stroke based on the pathophysiological mechanisms in the penumbra has yet to be achieved. Recent findings shape the modern understanding of the penumbra revealing a plethora of molecular and cellular pathophysiological mechanisms. We now propose a new model of the penumbra, one which we hope will lay the foundation for future translational success. We focus on the availability of glucose, the brain's central source of energy, and bioenergetic failure as core pathophysiological concepts. We discuss the relation of mitochondrial function in different cell types to bioenergetics and apoptotic cell death mechanisms, autophagy, and neuroinflammation, to glucose metabolism in what is a dynamic ischemic penumbra.

Deciphering the Mysterious Relationship between the Cross-Pathogenetic Mechanisms of Neurodegenerative and Oncological Diseases

The relationship between oncological pathologies and neurodegenerative disorders is extremely complex and is a topic of concern among a growing number of researchers around the world. In recent years, convincing scientific evidence has accumulated that indicates the contribution of a number of etiological factors and pathophysiological processes to the pathogenesis of these two fundamentally different diseases, thus demonstrating an intriguing relationship between oncology and neurodegeneration. In this review, we establish the general links between three intersecting aspects of oncological pathologies and neurodegenerative disorders, i.e., oxidative stress, epigenetic dysregulation, and metabolic dysfunction, examining each process in detail to establish an unusual epidemiological relationship. We also focus on reviewing the current trends in the research and the clinical application of the most promising chemical structures and therapeutic platforms that have a modulating effect on the above processes. Thus, our comprehensive analysis of the set of molecular determinants that have obvious cross-functional pathways in the pathogenesis of oncological and neurodegenerative diseases can help in the creation of advanced diagnostic tools and in the development of innovative pharmacological strategies.

BAX activation in mouse retinal ganglion cells occurs in two temporally and mechanistically distinct steps

BACKGROUND

Pro-apoptotic BAX is a central mediator of retinal ganglion cell (RGC) death after optic nerve damage. BAX activation occurs in two stages including translocation of latent BAX to the mitochondrial outer membrane (MOM) and then permeabilization of the MOM to facilitate the release of apoptotic signaling molecules. As a critical component of RGC death, BAX is an attractive target for neuroprotective therapies and an understanding of the kinetics of BAX activation and the mechanisms controlling the two stages of this process in RGCs is potentially valuable in informing the development of a neuroprotective strategy.

METHODS

The kinetics of BAX translocation were assessed by both static and live-cell imaging of a GFP-BAX fusion protein introduced into RGCs using AAV2-mediated gene transfer in mice. Activation of BAX was achieved using an acute optic nerve crush (ONC) protocol. Live-cell imaging of GFP-BAX was achieved using explants of mouse retina harvested 7 days after ONC. Kinetics of translocation in RGCs were compared to GFP-BAX translocation in 661W tissue culture cells. Permeabilization of GFP-BAX was assessed by staining with the 6A7 monoclonal antibody, which recognizes a conformational change in this protein after MOM insertion. Assessment of individual kinases associated with both stages of activation was made using small molecule inhibitors injected into the vitreous either independently or in concert with ONC surgery. The contribution of the Dual Leucine Zipper-JUN-N-Terminal Kinase cascade was evaluated using mice with a double conditional knock-out of both Mkk4 and Mkk7.

RESULTS

ONC induces the translocation of GFP-BAX in RGCs at a slower rate and with less intracellular synchronicity than 661W cells, but exhibits less variability among mitochondrial foci within a single cell. GFP-BAX was also found to translocate in all compartments of an RGC including the dendritic arbor and axon. Approximately 6% of translocating RGCs exhibited retrotranslocation of BAX immediately following translocation. Unlike tissue culture cells, which exhibit simultaneous translocation and permeabilization, RGCs exhibited a significant delay between these two stages, similar to detached cells undergoing anoikis. Translocation, with minimal permeabilization could be induced in a subset of RGCs using an inhibitor of Focal Adhesion Kinase (PF573228). Permeabilization after ONC, in a majority of RGCs, could be inhibited with a broad spectrum kinase inhibitor (sunitinib) or a selective inhibitor for p38/MAPK14 (SB203580). Intervention of DLK-JNK axis signaling abrogated GFP-BAX translocation after ONC.

CONCLUSIONS

A comparison between BAX activation kinetics in tissue culture cells and in cells of a complex tissue environment shows distinct differences indicating that caution should be used when translating findings from one condition to the other. RGCs exhibit both a delay between translocation and permeabilization and the ability for translocated BAX to be retrotranslocated, suggesting several stages at which intervention of the activation process could be exploited in the design of a therapeutic strategy.

Neuroprotective compounds from marine invertebrates

Background

Neuroinflammation is a key pathological feature of a wide variety of neurological disorders, including Parkinson’s, multiple sclerosis, Alzheimer’s, and Huntington’s disease. While current treatments for these disorders are primarily symptomatic, there is a growing interest in developing new therapeutics that target the underlying neuroinflammatory processes.

Main body

Marine invertebrates, such as coral, sea urchins, starfish, sponges, and sea cucumbers, have been found to contain a wide variety of biologically active compounds that have demonstrated potential therapeutic properties. These compounds are known to target various key proteins and pathways in neuroinflammation, including 6-hydroxydopamine (OHDH), caspase-3 and caspase-9, p-Akt, p-ERK, p-P38, acetylcholinesterase (AChE), amyloid-β (Aβ), HSF-1, α-synuclein, cellular prion protein, advanced glycation end products (AGEs), paraquat (PQ), and mitochondria DJ-1.

Short conclusion

This review focuses on the current state of research on the neuroprotective effects of compounds found in marine invertebrates and the potential therapeutic implications of these findings for treating neuroinflammatory disorders. We also discussed the challenges and limitations of using marine-based compounds as therapeutics, such as sourcing and sustainability concerns, and the need for more preclinical and clinical studies to establish their efficacy and safety.

Graphical abstract

METTL3 Affects Spinal Cord Neuronal Apoptosis by Regulating Bcl-2 m6A Modifications After Spinal Cord Injury

OBJECTIVE

Spinal cord injury (SCI) is a severe type of neurological trauma. N6-methyladenosine (m6A) modification is one of the most common internal modifications of RNA. The role of METTL3, the predominant methylation enzyme of m6A modification, in SCI remains unclear. This study aimed to investigate the role of methyltransferase METTL3 in SCI.

METHODS

After establishing the oxygen-glucose deprivation (OGD) model of PC12 cells and rat spinal cord hemisection model, we found that the expression of METTL3 and the overall m6A modification level were significantly increased in neurons. The m6A modification was identified on B-cell lymphoma 2 (Bcl-2) messenger RNA (mRNA) by bioinformatics analysis, and m6A-RNA immunoprecipitation and RNA immunoprecipitation. In addition, METTL3 was blocked by the specific inhibitor STM2457 and gene knockdown, and then apoptosis levels were measured.

RESULTS

In different models, we found that the expression of METTL3 and the overall m6A modification level were significantly increased in neurons. After inducing OGD, inhibition of METTL3 activity or expression increased the mRNA and protein levels of Bcl-2, inhibited neuronal apoptosis, and improved neuronal viability in the spinal cord.

CONCLUSION

Inhibition of METTL3 activity or expression can inhibit the apoptosis of spinal cord neurons after SCI through the m6A/Bcl-2 signaling pathway.

BAX activation in mouse retinal ganglion cells occurs in two temporally and mechanistically distinct steps

Background Pro-apoptotic BAX is a central mediator of retinal ganglion cell (RGC) death after optic nerve damage. BAX activation occurs in two stages including translocation of latent BAX to the mitochondrial outer membrane (MOM) and then permeabilization of the MOM to facilitate the release of apoptotic signaling molecules. As a critical component of RGC death, BAX is an attractive target for neuroprotective therapies and an understanding of the kinetics of BAX activation and the mechanisms controlling the two stages of this process in RGCs is potentially valuable in informing the development of a neuroprotective strategy. Methods The kinetics of BAX translocation were assessed by both static and live-cell imaging of a GFP-BAX fusion protein introduced into RGCs using AAV2-mediated gene transfer in mice. Activation of BAX was achieved using an acute optic nerve crush (ONC) protocol. Live-cell imaging of GFP-BAX was achieved using explants of mouse retina harvested 7 days after ONC. Kinetics of translocation in RGCs were compared to GFP-BAX translocation in 661W tissue culture cells. Permeabilization of GFP-BAX was assessed by staining with the 6A7 monoclonal antibody, which recognizes a conformational change in this protein after MOM insertion. Assessment of individual kinases associated with both stages of activation was made using small molecule inhibitors injected into the vitreous either independently or in concert with ONC surgery. The contribution of the Dual Leucine Zipper-JUN-N-Terminal Kinase cascade was evaluated using mice with a double conditional knock-out of both Mkk4 and Mkk7 . Results ONC induces the translocation of GFP-BAX in RGCs at a slower rate and with less intracellular synchronicity than 661W cells, but exhibits less variability among mitochondrial foci within a single cell. GFP-BAX was also found to translocate in all compartments of an RGC including the dendritic arbor and axon. Approximately 6% of translocating RGCs exhibited retrotranslocation of BAX immediately following translocation. Unlike tissue culture cells, which exhibit simultaneous translocation and permeabilization, RGCs exhibited a significant delay between these two stages, similar to detached cells undergoing anoikis. Translocation, with minimal permeabilization could be induced in a subset of RGCs using an inhibitor of Focal Adhesion Kinase (PF573228). Permeabilization after ONC, in a majority of RGCs, could be inhibited with a broad spectrum kinase inhibitor (sunitinib) or a selective inhibitor for p38/MAPK14 (SB203580). Intervention of DLK-JNK axis signaling abrogated GFP-BAX translocation after ONC. Conclusions A comparison between BAX activation kinetics in tissue culture cells and in cells of a complex tissue environment shows distinct differences indicating that caution should be used when translating findings from one condition to the other. RGCs exhibit both a delay between translocation and permeabilization and the ability for translocated BAX to be retrotranslocated, suggesting several stages at which intervention of the activation process could be exploited in the design of a therapeutic strategy.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

PERK inhibitor, GSK2606414, ameliorates neuropathological damage, memory and motor functional impairments in cerebral ischemia via PERK/p-eIF2ɑ/ATF4/CHOP signaling

The protein kinase R-like endoplasmic reticulum kinase/eukaryotic initiation factor 2ɑ (PERK/eIF2α), the branch of unfolded protein response (UPR), is responsible for transient arrest in translation to counter the enhanced levels of misfolded or unfolded proteins in the endoplasmic reticulum (ER) following any acute condition. In neurological disorders, overactivation of PERK-P/eIF2-P signaling, leads to a prolonged decline in global protein synthesis resulting in synaptic failure and neuronal death. Our study has shown, PERK/ATF4/CHOP pathway gets activated following cerebral ischemia in rats. We have further demonstrated, PERK inhibitor, GSK2606414 ameliorates ischemia induced neuronal damage by preventing additional neuronal loss, minimizing brain infarct, reducing brain edema, and preventing neurological symptoms from appearing. GSK2606414 was found to improve the neurobehavioral deficits and reduce the pyknotic neurons in ischemic rats. Also, it decreased glial activation and apoptotic protein mRNA expression while enhanced the synaptic protein mRNA expression in rat brain following cerebral ischemia. In conclusion, our findings suggest that PERK/ATF4/CHOP activation play a vital role in cerebral ischemia. Thus, PERK inhibitor, GSK2606414 might be a potential neuroprotective agent in cerebral ischemia.

Endoplasmic reticulum protein BIK binds to and inhibits mitochondria-localized antiapoptotic proteins

The proapoptotic BCL-2 homology (BH3)-only endoplasmic reticulum (ER)-resident protein BCL-2 interacting killer (BIK) positively regulates mitochondrial outer membrane permeabilization, the point of no return in apoptosis. It is generally accepted that BIK functions at a distance from mitochondria by binding and sequestering antiapoptotic proteins at the ER, thereby promoting ER calcium release. Although BIK is predominantly localized to the ER, we detect by fluorescence lifetime imaging microscopy-FRET microscopy, BH3 region-dependent direct binding between BIK and mitochondria-localized chimeric mutants of the antiapoptotic proteins BCL-XL and BCL-2 in both baby mouse kidney (BMK) and MCF-7 cells. Direct binding was accompanied by cell type-specific differential relocalization in response to coexpression of either BIK or one of its target binding partners, BCL-XL, when coexpressed in cells. In BMK cells with genetic deletion of both BAX and BAK (BMK-double KO), our data suggest that a fraction of BIK protein moves toward mitochondria in response to the expression of a mitochondria-localized BCL-XL mutant. In contrast, in MCF-7 cells, our data suggest that BIK is localized at both ER and mitochondria-associated ER membranes and binds to the mitochondria-localized BCL-XL mutant via relocalization of BCL-XL to ER and mitochondria-associated ER membrane. Rather than functioning at a distance, our data suggest that BIK initiates mitochondrial outer membrane permeabilization via direct interactions with ER and mitochondria-localized antiapoptotic proteins, which occur via ER-mitochondria contact sites, and/or by relocalization of either BIK or antiapoptotic proteins in cells.

An Atypical, Staged Cell Death Pathway Induced by Depletion of SNARE-Proteins MUNC18-1 or Syntaxin-1

The presynaptic proteins MUNC18-1, syntaxin-1, and SNAP25 drive SNARE-mediated synaptic vesicle fusion and are also required for neuronal viability. Their absence triggers rapid, cell-autonomous, neuron-specific degeneration, unrelated to synaptic vesicle deficits. The underlying cell death pathways remain poorly understood. Here, we show that hippocampi of munc18-1 null mice (unknown sex) express apoptosis hallmarks cleaved caspase 3 (CC-3) and phosphorylated p53, and have condensed nuclei. However, side-by-side in vitro comparison with classical apoptosis induced by camptothecin uncovered striking differences to syntaxin-1 and MUNC18-1 depleted neurons. First, live-cell imaging revealed consecutive neurite retraction hours before cell death in MUNC18-1 or syntaxin-1 depleted neurons, whereas all neurites retracted at once, directly before cell death in classical apoptosis. Second, CC-3 activation was observed only after loss of all neurites and cellular breakdown, whereas CC-3 is activated before any neurite loss in classical apoptosis. Third, a pan-caspase inhibitor and a p53 inhibitor both arrested classical apoptosis, as expected, but not cell death in MUNC18-1 or syntaxin-1 depleted neurons. Neuron-specific cell death, consecutive neurite retraction, and late CC-3 activation were conserved in syntaxin-1 depleted human neurons. Finally, no indications were observed for involvement of other established cell death pathways, including necroptosis, Wallerian degeneration, autophagic cell death, and pyroptosis. Together, these data show that depletion of presynaptic proteins MUNC18-1 or syntaxin-1 triggers an atypical, staged cell death pathway characterized by consecutive neurite retraction, ultimately leading to, but not driven by, apoptosis.SIGNIFICANCE STATEMENT Neuronal cell death can occur via a multitude of pathways and plays an important role in the developing nervous system as well as neurodegenerative diseases. One poorly understood pathway to neuronal cell death takes place on depletion of presynaptic SNARE proteins syntaxin-1, SNAP25, or MUNC18-1. The current study demonstrates that MUNC18-1 or syntaxin-1 depleted neurons show a new, atypical, staged cell death that does not resemble any of the established cell death pathways in neurons. Cell death on MUNC18-1 or syntaxin-1 depletion is characterized by consecutive neurite retraction, ultimately involving, but not driven by, classical apoptosis.

OL-FS13 Alleviates Cerebral Ischemia-reperfusion Injury by Inhibiting miR-21-3p Expression

BACKGROUND

OL-FS13, a neuroprotective peptide derived from Odorrana livida, can alleviate cerebral ischemia-reperfusion (CI/R) injury, although the specific underlying mechanism remains to be further explored.

OBJECTIVE

The effect of miR-21-3p on the neural-protective effects of OL-FS13 was examined.

METHODS

In this study, the multiple genome sequencing analysis, double luciferase experiment, RT-qPCR, and Western blotting were used to explore the mechanism of OL-FS13.

RESULTS

Showed that over-expression of miR-21-3p against the protective effects of OL-FS13 on oxygen- glucose deprivation/re-oxygenation (OGD/R)-damaged pheochromocytoma (PC12) cells and in CI/R-injured rats. miR-21-3p was then found to target calcium/calmodulin-dependent protein kinase 2 (CAMKK2), and its overexpression inhibited the expression of CAMKK2 and phosphorylation of its downstream adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK), thereby inhibiting the therapeutic effects of OL-FS13 on OGD/R and CI/R. Inhibition of CAMKK2 also antagonized up-regulated of nuclear factor erythroid 2-related factor 2 (Nrf-2) by OL-FS13, thereby abolishing the antioxidant activity of the peptide.

CONCLUSION

Our results showed that OL-FS13 alleviated OGD/R and CI/R by inhibiting miR-21-3p to activate the CAMKK2/AMPK/Nrf-2 axis.

The mechanisms of learning and memory impairment caused by nonylphenol: a narrative review based on in vivo and in vitro studies

Learning and memory play a fundamental role on brain cognitive functions which are crucial for human life. Nonylphenol (NP), a serious environmental pollutant over the world, is proven to be harmful for learning and memory mainly via diet exposure. Currently, besides the administrative restrictions for the use of NP, there are rarely other effective approaches against learning and memory impairment caused by NP. This review summarized the mechanisms underlying NP-induced learning and memory impairment according to in vivo and in vitro experiments. Based on the studies involved in behavior tests, these mechanisms were classified as oxidative stress, neurotransmitter disorder, synaptic plasticity impairment, and neuron injury. In addition, according to the studies which did not conduct behavior tests, the possible mechanisms underlying NP-induced learning and memory impairment were proposed as chronic inflammation and gut permeability increment. Furthermore, this review also revealed the demanding questions for the mechanism investigations and therapeutic methods. Notably, the summarized mechanisms might accelerate the prevention and remediation of NP-induced learning and memory impairment.

Proteomic-Based Approach Reveals the Involvement of Apolipoprotein A-I in Related Phenotypes of Autism Spectrum Disorder in the BTBR Mouse Model

Autism spectrum disorder (ASD) is a neurodevelopmental disorder. Abnormal lipid metabolism has been suggested to contribute to its pathogenesis. Further exploration of its underlying biochemical mechanisms is needed. In a search for reliable biomarkers for the pathophysiology of ASD, hippocampal tissues from the ASD model BTBR T+ Itpr3tf/J (BTBR) mice and C57BL/6J mice were analyzed, using four-dimensional (4D) label-free proteomic analysis and bioinformatics analysis. Differentially expressed proteins were significantly enriched in lipid metabolic pathways. Among them, apolipoprotein A-I (ApoA-I) is a hub protein and its expression was significantly higher in the BTBR mice. The investigation of protein levels (using Western blotting) also confirmed this observation. Furthermore, expressions of SphK2 and S1P in the ApoA-I pathway both increased. Using the SphK inhibitor (SKI-II), ASD core phenotype and phenotype-related protein levels of P-CREB, P-CaMKII, and GAD1 were improved, as shown via behavioral and molecular biology experiments. Moreover, by using SKI-II, we found proteins related to the development and function of neuron synapses, including ERK, caspase-3, Bax, Bcl-2, CDK5 and KCNQ2 in BTBR mice, whose levels were restored to protein levels comparable to those in the controls. Elucidating the possible mechanism of ApoA-I in ASD-associated phenotypes will provide new ideas for studies on the etiology of ASD.

Citronellol Prevents 6-OHDA-Induced Oxidative Stress, Mitochondrial Dysfunction, and Apoptosis in Parkinson Disease Model of SH-SY5Y Cells via Modulating ROS-NO, MAPK/ERK, and PI3K/Akt Signaling Pathways

Parkinson disease is a neurodegenerative disorder distinguished by dopaminergic shortage in the striatum and the accumulation of α-synuclein neuronal aggregates in the brains of patients. Since, there is no accurate treatment available for Parkinson disease, researches are designed to alleviate the pathognomonic symptoms such as neuroinflammation, oxidative stress, mitochondrial dysfunction, and apoptosis. Accordingly, a number of compounds have been reported to inhibit these pathognomonic symptoms. In this study, we have assessed the neuroprotective potential of citronellol against 6-OHDA-induced neurotoxicity in SH-SY5Y cells. The results found that citronellol treatment effectively hindered the cell death caused by 6-OHDA and thereby maintaining the cell viability in SH-SY5Y cells at 50 µg/mL concentration. As expected, the citronellol treatment significantly reduced the 6-OHDA-induced secretion of inflammatory factors (IL-1β, IL-6, and TNF-α), which was obtained through ELISA technique. Similarly, citronellol hindered the 6-OHDA-induced oxidative stress by lowering the intracellular ROS and NO level and MDA leakage along with increased expression of SOD level in SH-SY5Y cells. The JC-1 staining showed that 6-OHDA increased the number of green fluorescent dots with ruptured mitochondrial membrane potential, while citronellol increased the amount of red fluorescent, showing the rescue potential against the 6-OHDA-induced mitochondrial dysfunction. Furthermore, citronellol hampered the 6-OHDA-induced apoptosis via the suppression of Bcl-2/Bax pathway. The western blotting results hypothesized that citronellol rescued SH-SY5Y cells from 6-OHDA-induced neurotoxicity via modulating ROS-NO, MAPK/ERK, and PI3K/Akt signaling pathways. However, further clinical trials are required to verify the anti-Parkinson efficacy.

ASIC1a induces mitochondrial apoptotic responses in acute lung injury

AIM

This study aimed to investigate the promoting effect of acid-sensing ion channel 1a (ASIC1a) on lipopolysaccharide (LPS)-induced acute lung injury (ALI) and its mechanisms.

METHODS

In this experiment, the ALI rat model was induced by intratracheal injection of LPS, and the ASIC1a specific blocker psalmotoxin-1 (PcTx-1) was injected into the tail vein before LPS administration once. Western blot, immunofluorescence, immunohistochemistry and real-time PCR methods were used to detect ASIC1a and apoptosis-related proteins expressions in lung tissue and RLE-6TN rat type II alveolar epithelial cells. Confocal Laser Scanning Microscopy was used to detect Ca²⁺ fluorescence intensity in RLE-6TN cells.

RESULTS

PcTx-1 pretreatment not only inhibited the pathological changes of LPS-induced ALI in lung tissue, but also inhibited lung dysfunction. PcTx-1 also reduced the increased levels of the apoptosis-related proteins B-cell lymphoma-2-associated X (Bax) and cleaved cysteinyl aspartate specific proteinase 3 (Cleaved caspase-3) and increased the decreased level of B-cell lymphoma-2 (Bcl-2) in the lung tissue of the model group. LPS-induced changes in mitochondrial membrane potential and calcium influx in alveolar epithelial cells were also reversed by PcTx-1.

CONCLUSION

ASIC1a induces an apoptotic response in ALI through mitochondrial apoptosis.

β-Sitosterol & quercetin enhances brain development in iodine deficient rat models

BACKGROUND

Recently thyroid hormone studies on brain growth, development and activity are regaining popularity. Thyroid hormones have long been believed to play critical role in mammalian brain growth and maturation regulating facets of neuronal cell growth, proliferation and differentiation and further signaling and glial cell differentiation. Deficiency of these hormones in mother leads to mental retardation in the subsequent offspring's.

METHODS

In this presented study, brain development of iodine deficient rat models created through deficiency in feeding, mating and further selection. Young adult female wistar rats were induced with iodine deficiency and then mated with healthy male rats. These pregnant hypothyroid induced females were treated with β-sitosterol (150 mg/kg/day) and quercetin (150 mg/kg/day) alone and in combination for whole gestation period. Analysis were dealt with the genetic and histological studies of the pups brain. PCR based RNA analysis was also carried out. Histology was done using eosin and hematoxylin.

RESULTS

Positive impacts of the β-sitosterol and quercetin on the iodine deficient brain were observed upon histological and PCR analysis. Altogether, the analysis proves that combined doses of β-sitosterol and quercetin for normal brain development in iodine deficient infants hence can be potentially applied as therapeutics in iodine deficiency circumstances.

Modulatory effects of vitamin B3 and its derivative on the levels of apoptotic and vascular regulators and cytoskeletal proteins in diabetic rat brain as signs of neuroprotection

BACKGROUND

Beneficial effects of nicotinamide (NAm) and its derivates have been earlier shown in animal models of diabetes mellitus (DM), but the mechanisms of their neuroprotective activities are still largely unknown. The aim of the present study was to investigate if NAm and conjugate of nicotinic acid with gamma-aminobutyric acid (N-GABA) are able to modulate expression levels of apoptosis regulators, angiogenesis-related molecules, and specific cytoskeletal proteins in diabetic rat brain.

METHODS

After six weeks of streptozotocin induced type 1 DM, rats were daily administered either by NAm (100 mg/kg) or N-GABA (55 mg/kg) intraperitoneally for two weeks. Protein levels were assessed by western blot and immunohistochemistry.

RESULTS

Both NAm and N-GABA down-regulated NF-κB and Bax levels in diabetic rat brain, suggesting their anti-apoptotic activities. Tested compounds normalized VEGF and nNOS contents improving pro-angiogenic signaling reduced by hyperglycemia. Western blot showed marked up-regulation of astroglial marker GFAP and lowering neurofilament protein levels in DM group, confirmed immunohistochemically, indicating the development of reactive astrogliosis as a major response to diabetes-induced neurodegeneration. NAm had no effects on GFAP and Nf-L levels in the diabetic brain, while N-GABA increased their expression. Inversely, NAm and N-GABA dramatically reduced enhanced levels of GFAP and Nf-L found in the blood serum of diabetic rats, providing for the first time strong evidence for preserving blood-brain barrier integrity by studied compounds.

CONCLUSION

Thus, NAm and N-GABA may exert neuroprotective effects by decreasing pro-apoptotic regulators levels and improving expression of angiogenic and cytoskeletal proteins impaired by hyperglycemia in rat brain.

Effect of Enterococcus faecalis OG1RF on human calvarial osteoblast apoptosis

Background

Enterococcus faecalis is a dominant pathogen in the root canals of teeth with persistent apical periodontitis (PAP), and osteoblast apoptosis contributes to imbalanced bone remodelling in PAP. Here, we investigated the effect of E. faecalis OG1RF on apoptosis in primary human calvarial osteoblasts. Specifically, the expression of apoptosis-related genes and the role of anti-apoptotic and pro-apoptotic members of the BCL-2 family were examined.

Methods

Primary human calvarial osteoblasts were incubated with E. faecalis OG1RF at multiplicities of infection corresponding to infection time points. Flow cytometry, terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay, caspase-3/-8/-9 activity assay, polymerase chain reaction (PCR) array, and quantitative real-time PCR were used to assess osteoblast apoptosis.

Results

E. faecalis infection increased the number of early- and late-phase apoptotic cells and TUNEL-positive cells, decreased the mitochondrial membrane potential (ΔΨm), and activated the caspase-3/-8/-9 pathway. Moreover, of all 84 apoptosis-related genes in the PCR array, the expression of 16 genes was upregulated and that of four genes was downregulated in the infected osteoblasts. Notably, the mRNA expression of anti-apoptotic BCL2 was downregulated, whereas that of the pro-apoptotic BCL2L11, HRK, BIK, BMF, NOXA, and BECN1 and anti-apoptotic BCL2A1 was upregulated.

Conclusions

E. faecalis OG1RF infection triggered apoptosis in human calvarial osteoblasts, and BCL-2 family members acted as regulators of osteoblast apoptosis. Therefore, BCL-2 family members may act as potential therapeutic targets for persistent apical periodontitis.

Mechanistic insights gained from cell and molecular analysis of the neuroprotective potential of bioactive natural compounds in an immortalized hippocampal cell line

Evaluating novel compounds for neuroprotective effects in animal models of traumatic brain injury (TBI) is a protracted, labor-intensive and costly effort. However, the present lack of effective treatment options for TBI, despite decades of research, shows the critical need for alternative methods for screening new drug candidates with neuroprotective properties. Because natural products have been a leading source of new therapeutic agents for human diseases, we used an in vitro model of stretch injury to rapidly assess pro-survival effects of three bioactive compounds, two isolated from natural products (clovanemagnolol [CM], vinaxanthone [VX]) and the third, a dietary compound (pterostilbene [PT]) found in blueberries. The stretch injury experiments were not used to validate drug efficacy in a comprehensive manner but used primarily, as proof-of-principle, to demonstrate that the neuroprotective potential of each bioactive agent can be quickly assessed in an immortalized hippocampal cell line in lieu of comprehensive testing in animal models of TBI. To gain mechanistic insights into potential molecular mechanisms of neuroprotective effects, we performed a pathway-specific PCR array analysis of the effects of CM on the rat hippocampus and microRNA sequencing analysis of the effects of VX and PT on cultured hippocampal progenitor neurons. We show that the neuroprotective properties of these natural compounds are associated with altered expression of several genes or microRNAs that have functional roles in neurodegeneration or cell survival. Our approach could help in quickly assessing multiple natural products for neuroprotective properties and expedite the process of new drug discovery for TBI therapeutics.

Efficacy and specificity of inhibitors of BCL-2 family protein interactions assessed by affinity measurements in live cells

Cytoplasmic and membrane-bound BCL-2 family proteins regulate apoptosis, a form of programmed cell death, via dozens of binary protein interactions confounding measurement of the effects of inhibitors in live cells. In cancer, apoptosis is frequently dysregulated, and cell survival depends on antiapoptotic proteins binding to and inhibiting proapoptotic BH3 proteins. The clinical success of BH3 mimetic inhibitors of antiapoptotic proteins has spawned major efforts by the pharmaceutical industry to develop molecules with different specificities and higher affinities. Here, quantitative fast fluorescence lifetime imaging microscopy enabled comparison of BH3 mimetic drugs in trials and preclinical development by measuring drug effects on binding affinities of interacting protein pairs in live cells. Both selectivity and efficacy were assessed for 15 inhibitors of four antiapoptotic proteins for each of six BH3 protein ligands. While many drugs target the designed interaction, most also have unexpected selectivity and poor efficacy in cells.

Transcranial magnetic stimulation in animal models of neurodegeneration

Brain stimulation techniques offer powerful means of modulating the physiology of specific neural structures. In recent years, non-invasive brain stimulation techniques, such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation, have emerged as therapeutic tools for neurology and neuroscience. However, the possible repercussions of these techniques remain unclear, and there are few reports on the incisive recovery mechanisms through brain stimulation. Although several studies have recommended the use of non-invasive brain stimulation in clinical neuroscience, with a special emphasis on TMS, the suggested mechanisms of action have not been confirmed directly at the neural level. Insights into the neural mechanisms of non-invasive brain stimulation would unveil the strategies necessary to enhance the safety and efficacy of this progressive approach. Therefore, animal studies investigating the mechanisms of TMS-induced recovery at the neural level are crucial for the elaboration of non-invasive brain stimulation. Translational research done using animal models has several advantages and is able to investigate knowledge gaps by directly targeting neuronal levels. In this review, we have discussed the role of TMS in different animal models, the impact of animal studies on various disease states, and the findings regarding brain function of animal models after TMS in pharmacology research.

Neurofilament light protein as a biomarker in depression and cognitive function

PURPOSE OF REVIEW

Converging evidence suggest axonal damage is implicated in depression and cognitive function. Neurofilament light protein, measured within serum and cerebrospinal fluid, may be a biomarker of axonal damage. This article examines the emerging evidence implicating neurofilament light protein in depression and cognitive function.

RECENT FINDINGS

Preliminary cross-sectional and case-control studies in cohorts with depression have yielded inconsistent results regarding the association between neurofilament light protein and symptomatology. However, these studies had methodological limitations, requiring further investigation. Importantly, neurofilament light protein concentrations may be a marker of progression of cognitive decline and may be associated with cognitive performance within cognitively intact cohorts.

SUMMARY

Axonal damage is implicated in the neuropathology of depression and cognitive dysfunction. Consequently, neurofilament light protein is an emerging biomarker with potential in depression and cognitive function. Results are more consistent for cognition, requiring more research to assess neurofilament light protein in depression as well as other psychiatric disorders. Future longitudinal studies are necessary to determine whether neurofilament light protein can predict the onset and progression of depression and measure the effectiveness of potential psychiatric interventions and medications.

Tau aggregation and its relation to selected forms of neuronal cell death

How neurons die in neurodegenerative diseases is still unknown. The distinction between apoptosis as a genetically controlled mechanism, and necrosis, which was viewed as an unregulated process, has blurred with the ever-increasing number of necrotic-like death subroutines underpinned by genetically defined pathways. It is therefore pertinent to ask whether any of them apply to neuronal cell death in tauopathies. Although Alzheimer's disease (AD) is the most prevalent tauopathy, tauopathies comprise an array of over 30 diseases in which the cytoplasmic protein tau aggregates in neurons, and also, in some diseases, in glia. Animal models have sought to distil the contribution of tau aggregation to the cell death process but despite intensive research, no one mechanism of cell death has been unequivocally defined. The process of tau aggregation, and the fibrillar structures that form, touch on so many cellular functions that there is unlikely to be a simple linear pathway of death; as one is blocked another is likely to take the lead. It is timely to ask how far we have advanced into defining whether any of the molecular players in the new death subroutines participate in the death process. Here we briefly review the currently known cell death routines and explore what is known about their participation in tau aggregation-related cell death. We highlight the involvement of cell autonomous and the more recent non-cell autonomous pathways that may enhance tau-aggregate toxicity, and discuss recent findings that implicate microglial phagocytosis of live neurons with tau aggregates as a mechanism of death.

Loss of HCN2 in Dorsal Hippocampus of Young Adult Mice Induces Specific Apoptosis of the CA1 Pyramidal Neuron Layer

Neurons inevitably rely on a proper repertoire and distribution of membrane-bound ion-conducting channels. Among these proteins, the family of hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels possesses unique properties giving rise to the corresponding I_h-current that contributes to various aspects of neural signaling. In mammals, four genes (hcn1-4) encode subunits of HCN channels. These subunits can assemble as hetero- or homotetrameric ion-conducting channels. In order to elaborate on the specific role of the HCN2 subunit in shaping electrical properties of neurons, we applied an Adeno-associated virus (AAV)-mediated, RNAi-based knock-down strategy of hcn2 gene expression both in vitro and in vivo. Electrophysiological measurements showed that HCN2 subunit knock-down resulted in specific yet anticipated changes in I_h-current properties in primary hippocampal neurons and, in addition, corroborated that the HCN2 subunit participates in postsynaptic signal integration. To further address the role of the HCN2 subunit in vivo, we injected recombinant (r)AAVs into the dorsal hippocampus of young adult male mice. Behavioral and biochemical analyses were conducted to assess the contribution of HCN2-containing channels in shaping hippocampal network properties. Surprisingly, knock-down of hcn2 expression resulted in a severe degeneration of the CA1 pyramidal cell layer, which did not occur in mice injected with control rAAV constructs. This finding might pinpoint to a vital and yet unknown contribution of HCN2 channels in establishing or maintaining the proper function of CA1 pyramidal neurons of the dorsal hippocampus.

Mitochondrial dysfunction in Alzheimer's disease: Therapeutic implications of lithium

Alzheimer's disease (AD) is one of the most prevalent neurodegenerative diseases, characterized by the accumulation of abnormal tau proteins within neurons and amyloid plaques in the brain parenchyma, which leads to progressive loss of neurons in the brain. While the detailed mechanism of the pathogenesis of AD is still unknown, evidence suggests that mitochondrial dysfunction likely plays a fundamental role in the pathogenesis of this disease. Due to the relevance of mitochondrial alterations in AD, recent works have suggested the therapeutic potential of mitochondrial-targeted lithium. Lithium has been shown to possess neuroprotective and neurotrophic properties that could also be related to the upregulation of mitochondrial function. In the current work, we perform a comprehensive investigation of the significance of mitochondrial dysfunction in AD and pharmacological treatment with lithium as imperative in this pathology, through a brief review of the major findings on the effects of lithium as a therapeutic approach targeting mitochondria in the context of AD.

The role of Bcl-2 proteins in modulating neuronal Ca2+ signaling in health and in Alzheimer's disease

The family of B-cell lymphoma-2 (Bcl-2) proteins exerts key functions in cellular health. Bcl-2 primarily acts in mitochondria where it controls the initiation of apoptosis. However, during the last decades, it has become clear that this family of proteins is also involved in controlling intracellular Ca2+ signaling, a critical process for the function of most cell types, including neurons. Several anti- and pro-apoptotic Bcl-2 family members are expressed in neurons and impact neuronal function. Importantly, expression levels of neuronal Bcl-2 proteins are affected by age. In this review, we focus on the emerging roles of Bcl-2 proteins in neuronal cells. Specifically, we discuss how their dysregulation contributes to the onset, development, and progression of neurodegeneration in the context of Alzheimer's disease (AD). Aberrant Ca2+ signaling plays an important role in the pathogenesis of AD, and we propose that dysregulation of the Bcl-2-Ca2+ signaling axis may contribute to the progression of AD and that herein, Bcl-2 may constitute a potential therapeutic target for the treatment of AD.

Worms, Fat, and Death: Caenorhabditis elegans Lipid Metabolites Regulate Cell Death

Caenorhabditis elegans is well-known as the model organism used to elucidate the genetic pathways underlying the first described form of regulated cell death, apoptosis. Since then, C. elegans investigations have contributed to the further understanding of lipids in apoptosis, especially the roles of phosphatidylserines and phosphatidylinositols. More recently, studies in C. elegans have shown that dietary polyunsaturated fatty acids can induce the non-apoptotic, iron-dependent form of cell death, ferroptosis. In this review, we examine the roles of various lipids in specific aspects of regulated cell death, emphasizing recent work in C. elegans.