Mitochondrial calcium dysfunction contributes to autophagic cell death induced by MPP+ via AMPK pathway

Characterization and neurotherapeutic evaluation of venom polypeptides identified from Vespa magnifica: The role of Mastoparan-M in Parkinson's disease intervention

ETHNOPHARMACOLOGICAL RELEVANCE

Parkinson's disease (PD) is a common neurodegenerative disorder in the elderly, characterized by the loss of dopaminergic neurons in the substantia nigra and the formation of Lewy bodies. Hufeng Jiu from Vespa magnifica Smith, a traditional remedy used by the Chinese Jingpo minority, is documented in the Pharmacopoeia of China (2020) for treating rheumatic arthritis. Notably, recent research suggests that components of wasp venom (WV) from Vespa magnifica Smith, particularly polypeptides such as Mastoparan-M (Mast-M) and Vespakinin-M, may have potential therapeutic effects for neurological disorders. However, the specific polypeptide components of WV and their therapeutic effects on PD models remain insufficiently understood.

AIM OF THE STUDY

This study aims to characterize the neuroactive polypeptides in Vespa magnifica Smith venom and investigate the therapeutic potential of Mast-M for PD.

MATERIALS AND METHODS

Neuroactive polypeptides in WV were identified using LC/MS, and Mast-M derived from venom of Vespa magnifica Smith was verified with HPLC. The neuroprotective effects of WV and its peptides were assessed using the CCK-8 assay in 1-methyl-4- phenylpyridinium (MPP+)-induced SH-SY5Y human neuroblastoma cells. Mast-M was identified as a potent antagonist against MPP+-induced neurotoxicity. The toxicity, hemolytic activity, and blood-brain-barrier (BBB) permeability of Mast-M were evaluated in mice, and its therapeutic effects were assessed in an MPTP-induced PD mouse model, focusing on motor function and tyrosine hydroxylase (TH) levels. Additionally, Mast-M's impact on mitochondrial membrane potential (MMP), autophagy, and the AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) signling pathway was investigated.

RESULTS

A total of 1007 peptides were identified in the WV, including 187 UniProtKB unreviewed, with 185 predicted to be BBB-permeability. Our results show that Mast-M exhibits a time-dependent distribution in mice, initially localizing in the peritoneal region and subsequently accumulating in the brain, liver, and kidney. Cellular uptake studies reveal that Mast-M penetrates cell membranes and accumulates intracellularly over time. In the MPP+-induced neurotoxicity model using SH-SY5Y cells, Mast-M significantly enhances cell viability and MMP. In vivo safety assessments indicate that Mast-M is well-tolerated at doses up to 100 μg/kg, with no significant toxicological effects observed. However, higher doses induce hepatic distress, necessitating dose optimization. Hemolysis was absent at concentrations ≤37 μg/mL, with an EC50 for hemolytic activity of 197 μg/mL. In MPTP-induced PD models, Mast-M partially ameliorates motor deficits and preserves TH expression in dopaminergic neurons, supporting its neuroprotective role. Mechanistically, Mast-M activates autophagic pathways, as evidenced by the upregulation of autophagy-related protein LC3 in MPP+-challenged SH-SY5Y cells. Furthermore, Mast-M promotes mitophagy and mitochondrial biogenesis, modulating the AMPK/mTOR signaling axis to facilitate mitochondrial turnover.

CONCLUSION

Mast-M emerges as a promising therapeutic candidate for PD, capable of crossing the BBB, enhancing autophagy, and providing neuroprotection in PD models. Further studies are warranted to optimize dosing and elucidate its full therapeutic potential.

MCU complex: Exploring emerging targets and mechanisms of mitochondrial physiology and pathology

BACKGROUND

Globally, the onset and progression of multiple human diseases are associated with mitochondrial dysfunction and dysregulation of Ca2+ uptake dynamics mediated by the mitochondrial calcium uniporter (MCU) complex, which plays a key role in mitochondrial dysfunction. Despite relevant studies, the underlying pathophysiological mechanisms have not yet been fully elucidated.

AIM OF REVIEW

This article provides an in-depth analysis of the current research status of the MCU complex, focusing on its molecular composition, regulatory mechanisms, and association with diseases. In addition, we conducted an in-depth analysis of the regulatory effects of agonists, inhibitors, and traditional Chinese medicine (TCM) monomers on the MCU complex and their application prospects in disease treatment. From the perspective of medicinal chemistry, we conducted an in-depth analysis of the structure-activity relationship between these small molecules and MCU and deduced potential pharmacophores and binding pockets. Simultaneously, key structural domains of the MCU complex in Homo sapiens were identified. We also studied the functional expression of the MCU complex in Drosophila, Zebrafish, and Caenorhabditis elegans. These analyses provide a basis for exploring potential treatment strategies targeting the MCU complex and provide strong support for the development of future precision medicine and treatments.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The MCU complex exhibits varying behavior across different tissues and plays various roles in metabolic functions. It consists of six MCU subunits, an essential MCU regulator (EMRE), and solute carrier 25A23 (SLC25A23). They regulate processes, such as mitochondrial Ca2+ (mCa2+) uptake, mitochondrial adenosine triphosphate (ATP) production, calcium dynamics, oxidative stress (OS), and cell death. Regulation makes it a potential target for treating diseases, especially cardiovascular diseases, neurodegenerative diseases, inflammatory diseases, metabolic diseases, and tumors.

Curcumin prevents neurodegeneration by blocking HDAC6-NLRP3 pathway-dependent neuroinflammation in Parkinson's disease

Curcumin is a hydrophobic polyphenolic compound with potent anti-inflammatory properties. However, whether it can achieve therapeutic effects by alleviating neuroinflammation in patients with Parkinson's disease (PD) and its potential mechanism are still unknown. This study explored the effects of curcumin on neuroinflammation in dopaminergic neurons and deciphered its direct target in the histone deacetylase 6 (HDAC6)-Nucleotide-binding domain, leucine-rich repeat, and pyrin domain-containing protein 3 (NLRP3) pathway, revealing the potential role of curcumin in the treatment of Parkinson's disease. Here, we show that curcumin alleviated the degeneration of neurons in a PD model by mitigating the activation of the NLRP3-mediated inflammatory response both in vivo and in vitro. Furthermore, we discovered that curcumin prevented neuroinflammation by blocking the HDAC6-NLRP3 pathway in a PD model. Moreover, overexpression of HDAC6 could eliminate the effect of curcumin on the neuroinflammatory response mediated by NLRP3. Curcumin and the HDAC6 inhibitor WT161 could alleviate neurodegeneration. In addition, activated HDAC6 directly deacetylated NLRP3 at lysine 84 to maintain its stability, which increased the inflammatory response and promoted neurodegeneration. These findings show that curcumin, a neuroinflammation inhibitor, blocks neurodegeneration via the HDAC6-NLRP3 pathway and represents a potentially practical pharmacological approach for treating neuroinflammation-driven neurodegenerative diseases. For the first time, HDAC6 was shown to directly regulate the acetylation of NLRP3.

The mechanisms of Ca2+ regulating autophagy and its research progress in neurodegenerative diseases: A review

Neurodegenerative diseases are complex disorders that significantly challenge human health, with their incidence increasing with age. A key pathological feature of these diseases is the accumulation of misfolded proteins. The underlying mechanisms involve an imbalance in calcium homeostasis and disturbances in autophagy, indicating a likely correlation between them. As the most important second messenger, Ca2+ plays a vital role in regulating various cell activities, including autophagy. Different organelles within cells serve as Ca2+ storage chambers and regulate Ca2+ levels under different conditions. Ca2+ in these compartments can affect autophagy via Ca2+ channels or other related signaling proteins. Researchers propose that Ca2+ regulates autophagy through distinct signal transduction mechanisms, under normal or stressful conditions, and thereby contributing to the occurrence and development of neurodegenerative diseases. This review provides a systematic examination of the regulatory mechanisms of Ca2+ in cell membranes and different organelles, as well as its downstream pathways that influence autophagy and its implications for neurodegenerative diseases. This comprehensive analysis may facilitate the development of new drugs and provide more precise treatments for neurodegenerative diseases.

Role of Inflammation in the Development of COVID-19 to Parkinson's Disease

Background

The coronavirus disease 2019 (COVID-19) can lead to neurological symptoms such as headaches, confusion, seizures, hearing loss, and loss of smell. The link between COVID-19 and Parkinson's disease (PD) is being investigated, but more research is needed for a definitive connection.

Methods

Datasets GSE22491 and GSE164805 were selected to screen differentially expressed gene (DEG), and immune infiltration and gene set enrichment analysis (GSEA) of the DEG were performed. WGCNA analyzed the DEG and selected the intersection genes. Potential biological functions and signaling pathways were determined, and diagnostic genes were further screened using gene expression and receiver operating characteristic (ROC) curves. Screening and molecular docking of ibuprofen as a therapeutic target. The effectiveness of ibuprofen was verified by constructing a PD model in vitro, and constructing "COVID19-PD" signaling pathway, and exploring the role of angiotensin-converting enzyme 2 (ACE2) in PD.

Results

A total of 13 DEG were screened from the GSE36980 and GSE5281 datasets. Kyoto encyclopedia of genes and genomes (KEGG) analysis showed that the DEG were mainly associated with the hypoxia-inducible factor (HIF-1), epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor resistance, etc. After analysis, it is found that ibuprofen alleviates PD symptoms by inhibiting the expression of nuclear factor kappa-B (NF-κB), interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α). Based on signal pathway construction, the importance of ACE2 in COVID-19-induced PD has been identified. ACE2 is found to have widespread distribution in the brain. In the 1-methyl-4-phenyl-1,2,3,6-te-trahydropyridine (MPTP)-induced ACE2-null PD mice model, more severe motor and non-motor symptoms, increased NF-κB p65 and α-synuclein (α-syn) expression with significant aggregation, decreased tyrosine hydroxylase (TH), severe neuronal loss, and neurodegenerative disorders.

Conclusion

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection increases the risk of PD through an inflammatory environment and downregulation of ACE2, providing evidence for the molecular mechanism and targeted therapy associated with COVID-19 and PD.

Smart antioxidant function enhancing (SAFE) nucleic acid therapy for ROS-related chronic diseases and comorbidities

Reactive oxygen species (ROS)-mediated oxidative stress exacerbates chronic diseases such as organ damage and neurodegenerative disorders. The Keap1-Nrf2-ARE pathway is a widely distributed endogenous antioxidant system. However, ROS under redox homeostasis regulates a wide range of life activities. Therefore, smart scavenging of excess ROS under pathological conditions is essential to treat chronic diseases safely. This study reports a smart antioxidant function enhancement (SAFE) strategy. On-demand release of nucleic acid drugs in a pathological ROS environment smartly activates the endogenous antioxidant system, thereby smartly alleviating oxidative stress in an exogenous antioxidant-independent manner. Through structural modulation and ligand modification, we develop SAFE nanoparticles based on nanohybrid complexes (SAFE-complex) adapted to brain delivery of nucleic acid drugs. SAFE-complex with homogeneous monodisperse structure efficiently treat ROS-related neurodegenerative diseases while protecting the major organ from oxidative stress damage. Moreover, SAFE-complex can stabilize storage in the form of freeze-dried powder. These data indicate that SAFE nanoparticles hold promise for treating ROS-related chronic diseases and comorbidities through rational transformation.

Increased DNMT1 Involvement in the Activation of LO2 Cell Death Induced by Silver Nanoparticles via Promoting TFEB-Dependent Autophagy

The accumulation of exogenous silver nanoparticles (AgNPs) will terminally bring about liver injury, including cell death, where DNA methylation tends to be a crucial epigenetic modulator. The change in the cell autophagy level verified to be closely associated with hepatocyte death has been followed with wide interest. But the molecular toxicological mechanisms of AgNPs in relation to DNA methylation, autophagy, and cell death remain inconclusive. To address the issue above, in LO2 cells treated with increasing concentrations of AgNPs (0, 5, 10, and 20 μg/mL), a cell cytotoxicity assay was performed to analyze the level of cell death, which also helped to choose an optimal concentration for next experiments. An immunofluorescence assay was used to determine the autophagic flux as well as TFEB translocation, with qRT-PCR and western blot being used to analyze the expression level of autophagy-related genes and proteins. According to our findings, in the determination of cell viability, 20 μg/mL (AgNPs) was adopted as the best working concentration. LO2 cell death, autophagy, and TFEB nuclear translocation were induced by AgNPs, which could be inhibited by lysosome inhibitor chloroquine (CQ) or siRNA specific for TFEB. Moreover, AgNP exposure led to DNA hypermethylation, with DNMT1 taking part mainly, which could be obviously prevented by 5-Aza-2'-deoxycytidine (5-AzaC) or trichostatin A (TSA) treatment or DNMT1 knockout in LO2 cells. Our studies suggest that through TFEB-dependent cell autophagy, increased DNMT1 may facilitate cell death induced by AgNPs.

Autophagy and podocytopathy

Autophagy is a complex process of lysosomal-dependent degradation of unwanted cellular material. In response to endogenous or exogenous stimuli, autophagy is induced and regulated by two kinases: the AMP activated kinase and the mammalian target of rapamycin (mTOR). Cells activated by Unc-51-like kinase 1 form a double membrane complex that sequesters the cargo (phagophore) and elongates producing spherical vesicles (autophagosomes). These reach and fuse with lysosomes, which degrade the cargo (autolysosomes). The resulting macromolecules are released back and recycled in the cytosol for reuse. In the podocyte, autophagy is a homeostatic mechanism that contributes to the formation and preservation of the morphological and functional integrity of actin cytoskeleton. Podocytes, fenestrated endothelial cells and glomerular basement membrane compose the glomerular filtration barrier. Podocyte damage may cause dysfunction of the glomerular barrier, proteinuria and glomerulosclerosis in different glomerular diseases and particularly in so-called podocytopathies, namely minimal change disease and focal segmental glomerulosclerosis. Several drugs and molecules may activate autophagic function in murine models. Among them, aldosterone inhibitors, mineralocorticoid inhibitors and vitamin D3 were proven to protect podocyte from injury and reduce proteinuria in clinical studies. However, no clinical trial with autophagy regulators in podocytopathies has been conducted. Caution is needed with other autophagy activators, such as mTOR inhibitors and metformin, because of potential adverse events.

The mitochondrial uncoupling effects of nitazoxanide enhances cellular autophagy and promotes the clearance of α-synuclein: Potential role of AMPK-JNK pathway

Upregulation and aggregation of the pre-synaptic protein, α-synuclein plays a key role in Parkinson's disease (PD) and mitochondrial dysfunction was surmised to be an upstream event in the disease pathogenesis. Emerging reports identified the role of nitazoxanide (NTZ), an anti-helminth drug, in enhancing mitochondrial oxygen consumption rate (OCR) and autophagy. In the present study, we have examined the mitochondrial effects of NTZ in mediating cellular autophagy and subsequent clearance of both endogenous and pre-formed aggregates of α-synuclein in cellular model of PD. Our results demonstrate that the mitochondrial uncoupling effects of NTZ results in the activation of AMPK and JNK, which in-turn leads to the enhancement of cellular autophagy. Also,1-methyl-4-phenylpyridinium (MPP⁺) mediated decrease in autophagic flux with a concomitant increase in the α-synuclein levels were ameliorated in cells treated with NTZ. However, in cells lacking functional mitochondria (ρ0 cells), NTZ did not mitigate MPP⁺ mediated alterations in the autophagic clearance of α-synuclein, indicating that the mitochondrial effects of NTZ play a crucial role in the clearance of α-synuclein by autophagy. Also, the ability of AMPK inhibitor, compound C, in abrogating NTZ mediated enhancement in the autophagic flux and α-synuclein clearance highlight the pivotal role of AMPK in NTZ mediated autophagy. Further, NTZ per se enhanced the clearance of preformed α-synuclein aggregates that were exogenously added to the cells. Overall, the results of our present study suggest that NTZ activates macroautophagy in cells due to its uncoupling effects on mitochondrial respiration via activation of AMPK-JNK pathway resulting in the clearance of both endogenous and pre-formed α-synuclein aggregates. As NTZ happens to possess good bioavailability and safety profile, considering this drug for PD based on its mitochondrial uncoupling and autophagy enhancing properties for mitigating mitochondrial reactive oxygen species (ROS) and α-synuclein toxicity appears to be a promising therapeutic option.

Effects of an Exercise Program Combining Aerobic and Resistance Training on Protein Expressions of Neurotrophic Factors in Obese Rats Injected with Beta-Amyloid

In this study, the effects of a 12-week exercise program combining aerobic and resistance training on high-fat diet-induced obese Sprague Dawley (SD) rats after the injection of beta-amyloid into the cerebral ventricle were investigated. Changes in physical fitness, cognitive function, blood levels of beta-amyloid and metabolic factors, and protein expressions of neurotrophic factors related to brain function such as BDNF (brain-derived neurotrophic factor) in the quadriceps femoris, hippocampus, and cerebral cortex were analyzed. The subjects were thirty-two 10-week-old SD rats (DBL Co., Ltd., Seoul, Korea). The rats were randomized into four groups: β-Non-Ex group (n = 8) with induced obesity and βA25-35 injection into the cerebral ventricle through stereotactic biopsy; β-Ex group (n = 8) with induced obesity, βA25-35 injection, and exercise; S-Non-Ex group (n = 8) with an injection of saline in lieu of βA25-35 as the control; and S-Ex group (n = 8) with saline injection and exercise. The 12-week exercise program combined aerobic training and resistance training. As for protein expressions of the factors related to brain function, the combined exercise program was shown to have a clear effect on activating the following factors: PGC-1α (peroxisome proliferator-activated receptor gamma coactivator 1-alpha), FNDC5 (fibronectin type III domain-containing protein 5), and BDNF in the quadriceps femoris; TrkB (Tropomyosin receptor kinase B), FNDC5, and BDNF in the hippocampus; PGC-1α, FNDC5, and BDNF in the cerebral cortex. The protein expression of β-amyloid in the cerebral cortex was significantly lower in the β-Ex group than in the β-Non-Ex group (p < 0.05). The 12-week intervention with the combined exercise program of aerobic and resistance training was shown to improve cardiopulmonary function, muscular endurance, and short-term memory. The results demonstrate a set of positive effects of the combined exercise program, which were presumed to have arisen mainly due to its alleviating effect on β-amyloid plaques, the main cause of reduced brain function, as well as the promotion of protein expressions of PGC-1α, FNDC5, and BDNF in the quadriceps femoris, hippocampus, and cerebral cortex.

Mitochondrial calcium exchange in physiology and disease

The uptake of calcium into and extrusion of calcium from the mitochondrial matrix is a fundamental biological process that has critical effects on cellular metabolism, signaling, and survival. Disruption of mitochondrial calcium (mCa2+) cycling is implicated in numerous acquired diseases such as heart failure, stroke, neurodegeneration, diabetes, and cancer and is genetically linked to several inherited neuromuscular disorders. Understanding the mechanisms responsible for mCa2+ exchange therefore holds great promise for the treatment of these diseases. The past decade has seen the genetic identification of many of the key proteins that mediate mitochondrial calcium uptake and efflux. Here, we present an overview of the phenomenon of mCa2+ transport and a comprehensive examination of the molecular machinery that mediates calcium flux across the inner mitochondrial membrane: the mitochondrial uniporter complex (consisting of MCU, EMRE, MICU1, MICU2, MICU3, MCUB, and MCUR1), NCLX, LETM1, the mitochondrial ryanodine receptor, and the mitochondrial permeability transition pore. We then consider the physiological implications of mCa2+ flux and evaluate how alterations in mCa2+ homeostasis contribute to human disease. This review concludes by highlighting opportunities and challenges for therapeutic intervention in pathologies characterized by aberrant mCa2+ handling and by summarizing critical unanswered questions regarding the biology of mCa2+ flux.

Autophagy and apoptosis cascade: which is more prominent in neuronal death?

Autophagy and apoptosis are two crucial self-destructive processes that maintain cellular homeostasis, which are characterized by their morphology and regulated through signal transduction mechanisms. These pathways determine the fate of cellular organelle and protein involved in human health and disease such as neurodegeneration, cancer, and cardiovascular disease. Cell death pathways share common molecular mechanisms, such as mitochondrial dysfunction, oxidative stress, calcium ion concentration, reactive oxygen species, and endoplasmic reticulum stress. Some key signaling molecules such as p53 and VEGF mediated angiogenic pathway exhibit cellular and molecular responses resulting in the triggering of apoptotic and autophagic pathways. Herein, based on previous studies, we describe the intricate relation between cell death pathways through their common genes and the role of various stress-causing agents. Further, extensive research on autophagy and apoptotic machinery excavates the implementation of selective biomarkers, for instance, mTOR, Bcl-2, BH3 family members, caspases, AMPK, PI3K/Akt/GSK3β, and p38/JNK/MAPK, in the pathogenesis and progression of neurodegenerative diseases. This molecular phenomenon will lead to the discovery of possible therapeutic biomolecules as a pharmacological intervention that are involved in the modulation of apoptosis and autophagy pathways. Moreover, we describe the potential role of micro-RNAs, long non-coding RNAs, and biomolecules as therapeutic agents that regulate cell death machinery to treat neurodegenerative diseases. Mounting evidence demonstrated that under stress conditions, such as calcium efflux, endoplasmic reticulum stress, the ubiquitin-proteasome system, and oxidative stress intermediate molecules, namely p53 and VEGF, activate and cause cell death. Further, activation of p53 and VEGF cause alteration in gene expression and dysregulated signaling pathways through the involvement of signaling molecules, namely mTOR, Bcl-2, BH3, AMPK, MAPK, JNK, and PI3K/Akt, and caspases. Alteration in gene expression and signaling cascades cause neurotoxicity and misfolded protein aggregates, which are characteristics features of neurodegenerative diseases. Excessive neurotoxicity and misfolded protein aggregates lead to neuronal cell death by activating death pathways like autophagy and apoptosis. However, autophagy has a dual role in the apoptosis pathways, i.e., activation and inhibition of the apoptosis signaling. Further, micro-RNAs and LncRNAs act as pharmacological regulators of autophagy and apoptosis cascade, whereas, natural compounds and chemical compounds act as pharmacological inhibitors that rescue neuronal cell death through inhibition of apoptosis and autophagic cell death.

Neurotoxicity and Underlying Mechanisms of Endogenous Neurotoxins

Endogenous and exogenous neurotoxins are important factors leading to neurodegenerative diseases. In the 1980s, the discovery that 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) contributes to Parkinson's disease (PD) symptoms led to new research investigations on neurotoxins. An abnormal metabolism of endogenous substances, such as condensation of bioamines with endogenous aldehydes, dopamine (DA) oxidation, and kynurenine pathway, can produce endogenous neurotoxins. Neurotoxins may damage the nervous system by inhibiting mitochondrial activity, increasing oxidative stress, increasing neuroinflammation, and up-regulating proteins related to cell death. This paper reviews the biological synthesis of various known endogenous neurotoxins and their toxic mechanisms.

Antagonizing effects of curcumin against mercury-induced autophagic death and trace elements disorder by regulating PI3K/AKT and Nrf2 pathway in the spleen

Mercury is a naturally occurring element and highly toxic to humans even at a low dosage. Curcumin is a polyphenol found in turmeric (Curcuma longa), widely used as a treatment strategy to improve antioxidant and anti-inflammatory properties. The purpose of this study was to investigate the potential protective mechanisms of curcumin in spleen damage induced by HgCl₂. The mice were given curcumin by intragastric administration 2 h before HgCl₂ injection for 24 h. At first, splenic transcriptome analysis showed that 3334 genes (2134 up and 1200 down) were differently expressed in HgCl₂-induced spleen damage model. Notably, KEGG enrichment showed phosphatidylinositol 3-kinase (PI3K)-AKT might be a key signaling pathways in HgCl₂-induced spleen damage. Furthermore, our data demonstrated that HgCl₂ could induce autophagic cell death, evidenced by increases the protein expression of PI3K, AKT, LC3-II and p62 and the number of apoptotic cells. Furthermore, we found that curcumin significantly combated autophagic cell death, sodium overload and calcium leak induced by HgCl₂. Simultaneously, further studies demonstrated that curcumin significantly activated nuclear factor (erythroid-derived-2)-like 2 (Nrf2) signaling pathway, and subsequent enhancing antioxidant defenses. Taken together, our data indicated that inorganic mercury could result in autophagic cell death, which may be related to the regulation of PI3K-AKT signaling cascades. Furthermore, Nrf2-mediated antioxidant defenses may be the target of curcumin to confers an adaptive survival response to resist spleen damage induced by HgCl₂. The present study perfects the mechanism theory of HgCl₂-induced spleen damage and provides a way for pharmacological intervention to prevent spleen injury.

Promising drug targets and associated therapeutic interventions in Parkinson's disease

Parkinson's disease (PD) is one of the most debilitating brain diseases. Despite the availability of symptomatic treatments, response towards the health of PD patients remains scarce. To fulfil the medical needs of the PD patients, an efficacious and etiological treatment is required. In this review, we have compiled the information covering limitations of current therapeutic options in PD, novel drug targets for PD, and finally, the role of some critical beneficial natural products to control the progression of PD.

Potentials of autophagy enhancing natural products in the treatment of Parkinson disease

Parkinson disease (PD) is a progressive neurodegenerative movement disorder characterized by motor and non-motor symptoms due to loss of striatal dopaminergic neurons and disruption of degradation signaling leading to the formation of Lewy bodies (aggregation of α-synuclein). Presently, there are no disease modifying therapy for PD despite improvement in the understanding of the disease pathogenesis. However, the drugs currently used in PD management provide symptomatic relieve for motor symptoms without significant improvement in non-motor complications, thus, a public health burden on caregivers and healthcare systems. There is therefore the need to discover disease modifying therapy with strong potential to halt the disease progression. Recent trend has shown that the dysfunction of lysosomal-autophagy pathway is highly implicated in PD pathology, hence, making autophagy a key player owing to its involvement in degradation and clearance of misfolded α-synuclein (a major hallmark in PD pathology). In this review, we described the current drugs/strategy in the management of PD including targeting the autophagy pathway as a novel approach that could serve as potential intervention for PD management. The discovery of small molecules or natural products capable of enhancing autophagy mechanism could be a promising strategy for PD treatment.

Potentials of autophagy enhancing natural products in the treatment of Parkinson disease

Parkinson disease (PD) is a progressive neurodegenerative movement disorder characterized by motor and non-motor symptoms due to loss of striatal dopaminergic neurons and disruption of degradation signaling leading to the formation of Lewy bodies (aggregation of α-synuclein). Presently, there are no disease modifying therapy for PD despite improvement in the understanding of the disease pathogenesis. However, the drugs currently used in PD management provide symptomatic relieve for motor symptoms without significant improvement in non-motor complications, thus, a public health burden on caregivers and healthcare systems. There is therefore the need to discover disease modifying therapy with strong potential to halt the disease progression. Recent trend has shown that the dysfunction of lysosomal-autophagy pathway is highly implicated in PD pathology, hence, making autophagy a key player owing to its involvement in degradation and clearance of misfolded α-synuclein (a major hallmark in PD pathology). In this review, we described the current drugs/strategy in the management of PD including targeting the autophagy pathway as a novel approach that could serve as potential intervention for PD management. The discovery of small molecules or natural products capable of enhancing autophagy mechanism could be a promising strategy for PD treatment.

Arsenic induces autophagy-dependent apoptosis via Akt inactivation and AMPK activation signaling pathways leading to neuronal cell death

Inorganic arsenic (As³⁺), a well-known worldwide industrial and environmental pollutant, has been linked to neurodegenerative disorders (NDs). Autophagy plays an important role in controlling neuronal cell survival/death. However, limited information is available regarding the toxicological mechanism at the interplay between autophagy and As³⁺-induced neurotoxicity. The present study found that As³⁺ exposure induced a concomitant activation of apoptosis and autophagy in Neuro-2a cells, which was accompanied with the increase of phosphatidylserine exposure on outer membrane leaflets and apoptotic cell population, and the activation of caspase-3, -7, and PARP as well as the elevation of protein expressions of LC3-II, Atg-5, and Beclin-1, and the accumulation of autophagosome. Pretreatment of cells with autophagy inhibitor 3-MA, but not that of Z-VAD-FMK (a pan-caspase inhibitor), effectively prevented the As³⁺-induced autophagic and apoptotic responses, indicating that As³⁺-triggered autophagy was contributing to neuronal cell apoptosis. Furthermore, As³⁺ exposure evoked the dephosphorylation of Akt. Pretreatment with SC79, an Akt activator, could significantly attenuated As³⁺-induced Akt inactivation as well as autophagic and apoptotic events. Expectedly, inhibition of Akt signaling with LY294002 obviously enhanced As³⁺-triggered autophagy and apoptosis. Exposure to As³⁺ also dramatically increased the phosphorylation level of AMPKα. Pretreatment of AMPK inhibitor (Compound C) could markedly abrogate the As³⁺-induced phosphorylated AMPKα expression, and autophagy and apoptosis activation. Taken together, these results indicated that As³⁺ exerted its cytotoxicity in neuronal cells via the Akt inactivation/AMPK activation downstream-regulated autophagy-dependent apoptosis pathways, which ultimately lead to cell death. Our findings suggest that the regulation of Akt/AMPK signals may be a promising intervention to against As³⁺-induced neurotoxicity and NDs.

Autophagic Cell Death During Development - Ancient and Mysterious

While cell death is a normal and essential component of development and homeostasis, dysregulation of this process underlies most human diseases, including cancer, autoimmunity and neurodegeneration. The best characterized mechanism for cell death is apoptosis, although some cells die by a distinct process known as autophagy-dependent cell death (ADCD). Autophagy is mediated by the formation of double membrane vesicles that contain protein aggregates, damaged organelles like mitochondria, and bulk cytoplasm, which then fuse with lysosomes to degrade and recycle their contents. Autophagy is typically viewed as an adaptive process that allows cells to survive stresses like nutrient deprivation, although increasing evidence suggests that it may also mediate cell death during development and pathogenesis. An aggressive form of autophagy termed autosis has been described in cells following either ischemia/reperfusion injury or in response to autophagy-inducing proteins like Tat-Beclin 1. Despite an extensive literature on autophagic cell death in a variety of contexts, there are still fundamental gaps in our understanding of this process. As examples: Does autophagy directly kill cells and if so how? Is ADCD activated concurrently when cells are triggered to die via apoptosis? And is ADCD essentially a more protracted version of autosis or a distinct pathway? The goal of this mini-review is to summarize the field and to identify some of the major gaps in our knowledge. Understanding the molecular mechanisms that mediate ADCD will not only provide new insights into development, they may facilitate the creation of better tools for both the diagnostics and treatment of disease.

Ion Channels and Transporters in Autophagy

Ion exchange between intracellular and extracellular spaces is the basic mechanism for controlling cell metabolism and signal transduction. This process is mediated by ion channels and transporters on the plasma membrane, or intracellular membranes that surround various organelles, in response to environmental stimuli. Macroautophagy (hereafter referred to as autophagy) is one of the lysosomal-dependent degradation pathways that maintains homeostasis through the degradation and recycling of cellular components (e.g., dysfunctional proteins and damaged organelles). Although autophagy-related (ATG) proteins play a central role in regulating the formation of autophagy-related member structures (e.g., phagophores, autophagosomes, and autolysosomes), the autophagic process also involves changes in expression and function of ion channels and transporters. Here we discuss current knowledge of the mechanisms that regulate autophagy in mammalian cells, with special attention to the ion channels and transporters. We also highlight prospects for the development of drugs targeting ion channels and transporters in autophagy.

Intricate role of mitochondrial calcium signalling in mitochondrial quality control for regulation of cancer cell fate

Mitochondrial quality control is crucial for sustaining cellular maintenance. Mitochondrial Ca²⁺ plays an important role in the maintenance of mitochondrial quality control through regulation of mitochondrial dynamics, mitophagy and mitochondrial biogenesis for preserving cellular homeostasis. The regulation of this dynamic interlink between these mitochondrial networks and mitochondrial Ca²⁺ appears indispensable for the adaptation of cells under external stimuli. Moreover, dysregulation of mitochondrial Ca²⁺ divulges impaired mitochondrial control that results in several pathological conditions such as cancer. Hence this review untangles the interplay between mitochondrial Ca²⁺ and quality control that govern mitochondrial health and mitochondrial coordinates in the development of cancer.

Targeting Multiple Myeloma through the Biology of Long-Lived Plasma Cells

Multiple myeloma (MM) is a hematological malignancy of terminally differentiated bone marrow (BM) resident B lymphocytes known as plasma cells (PC). PC that reside in the bone marrow include a distinct population of long-lived plasma cells (LLPC) that have the capacity to live for very long periods of time (decades in the human population). LLPC biology is critical for understanding MM disease induction and progression because MM shares many of the same extrinsic and intrinsic survival programs as LLPC. Extrinsic survival signals required for LLPC survival include soluble factors and cellular partners in the bone marrow microenvironment. Intrinsic programs that enhance cellular fidelity are also required for LLPC survival including increased autophagy, metabolic fitness, the unfolded protein response (UPR), and enhanced responsiveness to endoplasmic reticulum (ER) stress. Targeting LLPC cell survival mechanisms have led to standard of care treatments for MM including proteasome inhibition (Bortezomib), steroids (Dexamethasone), and immunomodulatory drugs (Lenalidomide). MM patients that relapse often do so by circumventing LLPC survival pathways targeted by treatment. Understanding the mechanisms by which LLPC are able to survive can allow us insight into the treatment of MM, which allows for the enhancement of therapeutic strategies in MM both at diagnosis and upon patient relapse.

The pore-forming subunit MCU of the mitochondrial Ca2+ uniporter is required for normal glucose-stimulated insulin secretion in vitro and in vivo in mice

AIMS/HYPOTHESIS

Mitochondrial oxidative metabolism is central to glucose-stimulated insulin secretion (GSIS). Whether Ca²⁺ uptake into pancreatic beta cell mitochondria potentiates or antagonises this process is still a matter of debate. Although the mitochondrial Ca²⁺ importer (MCU) complex is thought to represent the main route for Ca²⁺ transport across the inner mitochondrial membrane, its role in beta cells has not previously been examined in vivo.

METHODS

Here, we inactivated the pore-forming subunit of the MCU, encoded by Mcu, selectively in mouse beta cells using Ins1^Cre-mediated recombination. Whole or dissociated pancreatic islets were isolated and used for live beta cell fluorescence imaging of cytosolic or mitochondrial Ca²⁺ concentration and ATP production in response to increasing glucose concentrations. Electrophysiological recordings were also performed on whole islets. Serum and blood samples were collected to examine oral and i.p. glucose tolerance.

RESULTS

Glucose-stimulated mitochondrial Ca²⁺ accumulation (p< 0.05), ATP production (p< 0.05) and insulin secretion (p< 0.01) were strongly inhibited in beta cell-specific Mcu-null (βMcu-KO) animals, in vitro, as compared with wild-type (WT) mice. Interestingly, cytosolic Ca²⁺ concentrations increased (p< 0.001), whereas mitochondrial membrane depolarisation improved in βMcu-KO animals. βMcu-KO mice displayed impaired in vivo insulin secretion at 5 min (p< 0.001) but not 15 min post-i.p. injection of glucose, whilst the opposite phenomenon was observed following an oral gavage at 5 min. Unexpectedly, glucose tolerance was improved (p< 0.05) in young βMcu-KO (<12 weeks), but not in older animals vs WT mice.

CONCLUSIONS/INTERPRETATION

MCU is crucial for mitochondrial Ca²⁺ uptake in pancreatic beta cells and is required for normal GSIS. The apparent compensatory mechanisms that maintain glucose tolerance in βMcu-KO mice remain to be established.

The Interplay between Ca2+ Signaling Pathways and Neurodegeneration

Calcium (Ca²⁺) homeostasis is essential for cell maintenance since this ion participates in many physiological processes. For example, the spatial and temporal organization of Ca²⁺ signaling in the central nervous system is fundamental for neurotransmission, where local changes in cytosolic Ca²⁺ concentration are needed to transmit information from neuron to neuron, between neurons and glia, and even regulating local blood flow according to the required activity. However, under pathological conditions, Ca²⁺ homeostasis is altered, with increased cytoplasmic Ca²⁺ concentrations leading to the activation of proteases, lipases, and nucleases. This review aimed to highlight the role of Ca²⁺ signaling in neurodegenerative disease-related apoptosis, where the regulation of intracellular Ca²⁺ homeostasis depends on coordinated interactions between the endoplasmic reticulum, mitochondria, and lysosomes, as well as specific transport mechanisms. In neurodegenerative diseases, alterations-increased oxidative stress, energy metabolism alterations, and protein aggregation have been identified. The aggregation of α-synuclein, β-amyloid peptide (Aβ), and huntingtin all adversely affect Ca²⁺ homeostasis. Due to the mounting evidence for the relevance of Ca²⁺ signaling in neuroprotection, we would focus on the expression and function of Ca²⁺ signaling-related proteins, in terms of the effects on autophagy regulation and the onset and progression of neurodegenerative diseases.

The importance of choosing a preclinical model that reflects what happens in Parkinson's disease

One of the major problems in the translation of successful preclinical results to clinical studies and new therapies in Parkinson's disease is the use of preclinical models based on exogenous neurotoxins that do not replicate what happens in the disease. The loss of dopaminergic neurons containing neuromelanin in Parkinson´s disease takes years, contrasting the very rapid degeneration induced by exogenous neurotoxins. We discuss the role of endogenous neurotoxins generated during dopamine oxidation and its possible use as new preclinical models for Parkinson´s disease.