Gradual alteration of mitochondrial structure and function by beta-amyloids: importance of membrane viscosity changes, energy deprivation, reactive oxygen species production, and cytochrome c release

Excited State Rotational Freedom Impacts Viscosity Sensitivity in Arylcyanoamide Fluorescent Molecular Rotor Dyes

The microviscosity of intracellular environments plays an important role in monitoring cellular function. Thus, the capability of detecting changes in viscosity can be utilized for the detection of different disease states. Viscosity-sensitive fluorescent molecular rotors are potentially excellent probes for these applications; however, the predictable relationships between chemical structural features and viscosity sensitivity are poorly understood. Here, we investigate a set of arylcyanoamide-based fluorescent probes and the effect of small aliphatic substituents on their viscosity sensitivity. We found that the location of the substituents and the type of π-network of the fluorophore can significantly affect the viscosity sensitivity of these fluorophores. Computational analysis supported the notion that the excited state rotational energy barrier plays a dominant role in the relative viscosity sensitivity of these fluorophores. These findings provide valuable insight into the design of molecular rotor-based fluorophores for viscosity measurement.

A FRET-based ratiometric fluorescent probe for sensing bisulfite/sulfite and viscosity and its applications in food, water samples and test strips

A FRET-based ratiometric dual-response fluorescent probe, CQI, constructed by combining quinolinium-indole as the acceptor and coumarin as the donor, was developed for sensing HSO3-/SO32- and viscosity. After the interaction of probe CQI with the analyte, we achieved a green channel for the response to HSO3-/SO32- and an orange channel for the response to viscosity. We comprehensively evaluated the ability of CQI to detect SO2 derivatives and viscosity using fluorescence spectroscopy. Probe CQI exhibited a large Stokes shift (196 nm), a high energy transfer efficiency (99.6 %) and a wide detection range (0-250 μM). The fluorescence intensity of the probe increased up to 14-fold with increasing viscosity, and CQI could detect the viscosity of food thickeners. More importantly, probe CQI could not only successfully monitor SO2 derivatives in various food and water samples, but also be prepared as bisulfite test strips.

Rofecoxib derivatives as NIR fluorescent probes for mitochondrial viscosity and in vivo imaging of Aβ plaques

Alzheimer's disease (AD) is a multifaceted neurodegenerative disorder for which the underlying causes remain largely unknown. Therefore, the development of imaging agents capable of detecting biomarkers associated with this disease is crucial. Dual-functional probes are particularly important as they can track two biomarkers at the same time and examine their interaction. Herein, Two red-emissive dual-functional fluorescent probes, RC-1 and RA-2, have been designed and synthesized based on the Rofecoxib scaffold. When probes (RC-1 and RA-2) are in viscous media or bound to Aβ aggregates, there is a dramatic enhancement in fluorescence emission due to the constraint of the twisted intramolecular charge transfer effect (TICT). RC-1 with ideal blood-brain barrier (BBB) penetrability enables visualization of Aβ plaques in vivo AD mice. These results suggest that RC-1 and RA-2 have the potential to serve as powerful fluorescence imaging agents for Aβ and mitochondria-related pathology in AD.

Rational construction and evaluation of a dual-functional near-infrared fluorescent probe for the imaging of Amyloid-β and mitochondrial viscosity

Alzheimer's disease is a fatal, incurable, chronic neurodegenerative disease. Diagnosis in its early and even preclinical stages will be beneficial for its prevention and treatment. In the accepted pathological theory, abnormal accumulation of Aβ protein and abnormal mitochondrial function, including changes in mitochondrial viscosity, is closely related to Alzheimer's disease. To date, rare fluorescent probes have been reported that can simultaneously image Aβ plaques and mitochondrial viscosity. Therefore, the development of a dual-functional fluorescent probe for real-time fluorescence imaging of Aβ plaques and mitochondrial viscosity is crucial to discover a novel approach and strategy for the treatment of Alzheimer's disease, and to understand the pathological process and crosstalk between different biomarkers of Alzheimer's disease. Herein, we rationally designed and synthesized a series of fluorescent probes QM-SF-1∼5 with dimethylamino-quinolinium as the skeleton and thiophene as the π bridge to connect the groups with different electron-push/pull capacities. Among them, QM-SF-2 exhibited excellent properties such as large Stokes shift (168 nm), near-infrared emission (689 nm), and high selectivity and sensitivity (limit of detection was 1.07 μM) to Aβ aggregate and mitochondrial viscosity changes, indicating its promising prospects as a dual-functional imaging tool in the pathological study of Alzheimer's disease.

Alzheimer's Amyloid-β Accelerates Cell Senescence and Suppresses SIRT1 in Human Neural Stem Cells

As a lifelong source of neurons, neural stem cells (NSCs) serve multiple crucial functions in the brain. The senescence of NSCs may be associated with the onset and progression of Alzheimer's disease (AD). Our study reveals a noteworthy finding, indicating that the AD-associated pathogenic protein amyloid-β (Aβ) substantially enhances senescence-related characteristics of human NSCs. These characteristics encompass the enhanced expression of p16 and p21, the upregulation of genes associated with the senescence-associated secretory phenotype (SASP), increased SA-β-gal activity, and the activation of the DNA damage response. Further studies revealed that Aβ treatment significantly downregulates the SIRT1 protein which plays a crucial role in regulating the aging process and decreases downstream PGC-1α and FOXO3. Subsequently, we found that SIRT1 overexpression significantly alleviates a range of Aβ-induced senescent markers in human NSCs. Taken together, our results uncover that Aβ accelerates cellular senescence in human NSCs, making SIRT1 a highly promising therapeutic target for senescent NSCs which may contribute to age-related neurodegenerative diseases, including AD.

The pro-oncogenic protein IF1 does not contribute to the Warburg effect and is not regulated by PKA in cancer cells

The endogenous inhibitor of mitochondrial F1Fo-ATPase (ATP synthase), IF1, has been shown to exert pro-oncogenic actions, including reprogramming of cellular energy metabolism (Warburg effect). The latter action of IF1 has been reported to be hampered by its PKA-dependent phosphorylation, but both reprogramming of metabolism and PKA-dependent phosphorylation are intensely debated. To clarify these critical issues, we prepared stably IF1-silenced clones and compared their bioenergetics with that of the three parental IF1-expressing cancer cell lines. All functional parameters: respiration rate, ATP synthesis rate (OXPHOS), and mitochondrial membrane potential were similar in IF1-silenced and control cells, clearly indicating that IF1 cannot inhibit the ATP synthase in cancer cells when the enzyme works physiologically. Furthermore, all cell types exposed to PKA modulators and energized with NAD+-dependent substrates or succinate showed similar OXPHOS rate regardless of the presence or absence of IF1. Therefore, our results rule out that IF1 action is modulated by its PKA-dependent phosphorylated/dephosphorylated state. Notably, cells exposed to a negative PKA modulator and energized with NAD+-dependent substrates showed a significant decrease of the OXPHOS rate matching previously reported inactivation of complex I. Overall, this study definitively demonstrates that IF1 inhibits neither mitochondrial ATP synthase nor OXPHOS in normoxic cancer cells and does not contribute to the Warburg effect. Thus, currently the protection of cancer cells from severe hypoxia/anoxia and apoptosis remain the only unquestionable actions of IF1 as pro-oncogenic factor that may be exploited to develop therapeutic approaches.

Mitochondrial dysfunction and neurological disorders: A narrative review and treatment overview

Mitochondria play a vital role in the nervous system, as they are responsible for generating energy in the form of ATP and regulating cellular processes such as calcium (Ca2+) signaling and apoptosis. However, mitochondrial dysfunction can lead to oxidative stress (OS), inflammation, and cell death, which have been implicated in the pathogenesis of various neurological disorders. In this article, we review the main functions of mitochondria in the nervous system and explore the mechanisms related to mitochondrial dysfunction. We discuss the role of mitochondrial dysfunction in the development and progression of some neurological disorders including Parkinson's disease (PD), multiple sclerosis (MS), Alzheimer's disease (AD), depression, and epilepsy. Finally, we provide an overview of various current treatment strategies that target mitochondrial dysfunction, including pharmacological treatments, phototherapy, gene therapy, and mitotherapy. This review emphasizes the importance of understanding the role of mitochondria in the nervous system and highlights the potential for mitochondrial-targeted therapies in the treatment of neurological disorders. Furthermore, it highlights some limitations and challenges encountered by the current therapeutic strategies and puts them in future perspective.

Mitochondria in health, disease, and aging

Mitochondria are well known as organelles responsible for the maintenance of cellular bioenergetics through the production of ATP. Although oxidative phosphorylation may be their most important function, mitochondria are also integral for the synthesis of metabolic precursors, calcium regulation, the production of reactive oxygen species, immune signaling, and apoptosis. Considering the breadth of their responsibilities, mitochondria are fundamental for cellular metabolism and homeostasis. Appreciating this significance, translational medicine has begun to investigate how mitochondrial dysfunction can represent a harbinger of disease. In this review, we provide a detailed overview of mitochondrial metabolism, cellular bioenergetics, mitochondrial dynamics, autophagy, mitochondrial damage-associated molecular patterns, mitochondria-mediated cell death pathways, and how mitochondrial dysfunction at any of these levels is associated with disease pathogenesis. Mitochondria-dependent pathways may thereby represent an attractive therapeutic target for ameliorating human disease.

Mitochondria: At the crossroads between mechanobiology and cell metabolism

Metabolism and mechanics are two key facets of structural and functional processes in cells, such as growth, proliferation, homeostasis and regeneration. Their reciprocal regulation has been increasingly acknowledged in recent years: external physical and mechanical cues entail metabolic changes, which in return regulate cell mechanosensing and mechanotransduction. Since mitochondria are pivotal regulators of metabolism, we review here the reciprocal links between mitochondrial morphodynamics, mechanics and metabolism. Mitochondria are highly dynamic organelles which sense and integrate mechanical, physical and metabolic cues to adapt their morphology, the organization of their network and their metabolic functions. While some of the links between mitochondrial morphodynamics, mechanics and metabolism are already well established, others are still poorly documented and open new fields of research. First, cell metabolism is known to correlate with mitochondrial morphodynamics. For instance, mitochondrial fission, fusion and cristae remodeling allow the cell to fine-tune its energy production through the contribution of mitochondrial oxidative phosphorylation and cytosolic glycolysis. Second, mechanical cues and alterations in mitochondrial mechanical properties reshape and reorganize the mitochondrial network. Mitochondrial membrane tension emerges as a decisive physical property which regulates mitochondrial morphodynamics. However, the converse link hypothesizing a contribution of morphodynamics to mitochondria mechanics and/or mechanosensitivity has not yet been demonstrated. Third, we highlight that mitochondrial mechanics and metabolism are reciprocally regulated, although little is known about the mechanical adaptation of mitochondria in response to metabolic cues. Deciphering the links between mitochondrial morphodynamics, mechanics and metabolism still presents significant technical and conceptual challenges but is crucial both for a better understanding of mechanobiology and for potential novel therapeutic approaches in diseases such as cancer.

Potential Harm of IQOS Smoke to Rat Liver

The Food and Drug Administration has recently classified the IQOS electronic cigarette as a modified-risk tobacco product. However, IQOS cigarettes still release various harmful constituents typical of conventional cigarettes (CCs), although the concentrations are markedly lower. Here, we investigated the damaging effects of IQOS smoking on the liver. Male Sprague Dawley rats were exposed, whole body, 5 days/week for 4 weeks to IQOS smoke (4 sticks/day), and hepatic xenobiotic metabolism, redox homeostasis and lipidomic profile were investigated. IQOS boosted reactive radicals and generated oxidative stress. Exposure decreased cellular reserves of total glutathione (GSH) but not GSH-dependent antioxidant enzymes. Catalase and xanthine oxidase were greater in the exposed group, as were various hepatic CYP-dependent monooxygenases (CYP2B1/2, CYP1A1, CYP2A1, CYP2E1-linked). Respiratory chain activity was unaltered, while the number of liver mitochondria was increased. IQOS exposure had an impact on the hepatic lipid profile. With regard to the expression of some MAP kinases commonly activated by CC smoking, IQOS increased the p-p38/p38 ratio, while erythroid nuclear transcription factor 2 (Nrf2) was negatively affected. Our data suggest that IQOS significantly impairs liver function, supporting the precautionary stance taken by the WHO toward the use of these devices, especially by young people and pregnant women.

Age-Dependent Alterations in Platelet Mitochondrial Respiration

Mitochondrial dysfunction is an important cellular hallmark of aging and neurodegeneration. Platelets are a useful model to study the systemic manifestations of mitochondrial dysfunction. To evaluate the age dependence of mitochondrial parameters, citrate synthase activity, respiratory chain complex activity, and oxygen consumption kinetics were assessed. The effect of cognitive impairment was examined by comparing the age dependence of mitochondrial parameters in healthy individuals and those with neuropsychiatric disease. The study found a significant negative slope of age-dependence for both the activity of individual mitochondrial enzymes (citrate synthase and complex II) and parameters of mitochondrial respiration in intact platelets (routine respiration, maximum capacity of electron transport system, and respiratory rate after complex I inhibition). However, there was no significant difference in the age-related changes of mitochondrial parameters between individuals with and without cognitive impairment. These findings highlight the potential of measuring mitochondrial respiration in intact platelets as a means to assess age-related mitochondrial dysfunction. The results indicate that drugs and interventions targeting mitochondrial respiration may have the potential to slow down or eliminate certain aging and neurodegenerative processes. Mitochondrial respiration in platelets holds promise as a biomarker of aging, irrespective of the degree of cognitive impairment.

A fluorescent probe for detecting mitochondrial viscosity and its application in distinguishing human breast cancer cells from normal ones

Mitochondrial viscosity is closely associated with intracellular physiological activities yet their abnormality will result in various diseases. In particular, viscosity in cancer cells is different from that in normal cells, which is thought to be an indicator for cancer diagnosis. However, there were few fluorescent probes able to distinguish homologous cancer and normal cells by detecting mitochondrial viscosity. Herein, we designed a viscosity-sensitive fluorescent probe (named NP) based on the twisting intramolecular charge transfer (TICT) mechanism. NP exhibited exquisite sensitivity to viscosity and selectivity to mitochondria and excellent photophysical properties, such as large Stokes shift and high molar extinction coefficient, which enables wash-free, high-fidelity and fast imaging mitochondria. Moreover, it was capable of detecting mitochondrial viscosity in living cells and tissue, as well as monitoring apoptosis process. Significantly, considering numerous breast cancer cases in every country of the world, NP was successfully applied to distinguish human breast cancer cells (MCF-7) from normal cells (MCF-10A) by difference in fluorescence intensity originated from abnormality in mitochondrial viscosity. All the results indicated that NP could serve as a robust tool for effectively detecting mitochondrial viscosity changes in-situ.

Recent progress in the development of fluorescent probes for imaging pathological oxidative stress

Oxidative stress is closely related to the physiopathology of numerous diseases. Reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive sulfur species (RSS) are direct participants and important biomarkers of oxidative stress. A comprehensive understanding of their changes can help us evaluate disease pathogenesis and progression and facilitate early diagnosis and drug development. In recent years, fluorescent probes have been developed for real-time monitoring of ROS, RNS and RSS levels in vitro and in vivo. In this review, conventional design strategies of fluorescent probes for ROS, RNS, and RSS detection are discussed from three aspects: fluorophores, linkers, and recognition groups. We introduce representative fluorescent probes for ROS, RNS, and RSS detection in cells, physiological/pathological processes (e.g., Inflammation, Drug Induced Organ Injury and Ischemia/Reperfusion Injury etc.), and specific diseases (e.g., neurodegenerative diseases, epilepsy, depression, diabetes and cancer, etc.). We then highlight the achievements, current challenges, and prospects for fluorescent probes in the pathophysiology of oxidative stress-related diseases.

GFP-based red-emissive fluorescent probes for dual imaging of β-amyloid plaques and mitochondrial viscosity

Alzheimer's disease (AD), with incurable neurodegenerative damage, has attracted growing interest in exploration of better AD biomarkers in its early diagnosis. Among various biomarkers, amyloid-β (Aβ) aggregates and mitochondrial viscosity are closely related to AD and their dual imaging might provide a potential and feasible strategy. In this work, five GFP-based red-emissive fluorescent probes were rationally designed and synthesized for selective detection of β-amyloid plaques and viscosity, among which C25e exhibited superior properties and could successfully image β-amyloid plaques and mitochondrial viscosity with different fluorescence wavelength signals "turn-on" at around 624 and 640 nm, respectively. Moreover, the staining of brain sections from a transgenic AD mouse showed that probe C25e showed higher selectivity and signal-to-noise ratio towards Aβ plaques than commercially-available Thio-S. In addition, the probe C25e was, for the first time, employed for monitoring amyloid-β induced mitochondrial viscosity changes. Therefore, this GFP-based red-emissive fluorescent probe C25e could serve as a dual-functional tool for imaging β-amyloid plaques and mitochondrial viscosity, which might provide a unique strategy for the early diagnosis of Alzheimer's disease.

Effect of β-amyloid on blood-brain barrier properties and function

The deposition of beta-amyloid (Aβ) aggregates in the brain, accompanied by impaired cognitive function, is a characteristic feature of Alzheimer's disease (AD). An important role in this process is played by vascular disorders, in particular, a disturbance of the blood-brain barrier (BBB). The BBB controls the entry of Aβ from plasma to the brain via the receptor for advanced glycation end products (RAGE) and the removal of brain-derived Aβ via the low-density lipoprotein receptor-related protein (LRP1). The balance between the input of Aβ to the brain from the periphery and its output is disturbed during AD. Aβ changes the redox-status of BBB cells, which in turn changes the functioning of mitochondria and disrupts the barrier function of endothelial cells by affecting tight junction proteins. Aβ oligomers have the greatest toxic effect on BBB cells, and oligomers are most rapidly transferred by transcytosis from the brain side of the BBB to the blood side. Both the cytotoxic effect of Aβ and the impairment of barrier function are partly due to the interaction of Aβ monomers and oligomers with membrane-bound RAGE. AD therapies based on the disruption of this interaction or the creation of decoys for Aβ are being developed. The question of the transfer of various Aβ isoforms through the BBB is important, since it can influence the development of AD. It is shown that the rate of input of Aβ40 and Aβ42 from the blood into the brain is different. The actual question of the transfer of pathogenic Aβ isoforms with post-translational modifications or mutations through the BBB still remains open.

Light, Water, and Melatonin: The Synergistic Regulation of Phase Separation in Dementia

The swift rise in acceptance of molecular principles defining phase separation by a broad array of scientific disciplines is shadowed by increasing discoveries linking phase separation to pathological aggregations associated with numerous neurodegenerative disorders, including Alzheimer’s disease, that contribute to dementia. Phase separation is powered by multivalent macromolecular interactions. Importantly, the release of water molecules from protein hydration shells into bulk creates entropic gains that promote phase separation and the subsequent generation of insoluble cytotoxic aggregates that drive healthy brain cells into diseased states. Higher viscosity in interfacial waters and limited hydration in interiors of biomolecular condensates facilitate phase separation. Light, water, and melatonin constitute an ancient synergy that ensures adequate protein hydration to prevent aberrant phase separation. The 670 nm visible red wavelength found in sunlight and employed in photobiomodulation reduces interfacial and mitochondrial matrix viscosity to enhance ATP production via increasing ATP synthase motor efficiency. Melatonin is a potent antioxidant that lowers viscosity to increase ATP by scavenging excess reactive oxygen species and free radicals. Reduced viscosity by light and melatonin elevates the availability of free water molecules that allow melatonin to adopt favorable conformations that enhance intrinsic features, including binding interactions with adenosine that reinforces the adenosine moiety effect of ATP responsible for preventing water removal that causes hydrophobic collapse and aggregation in phase separation. Precise recalibration of interspecies melatonin dosages that account for differences in metabolic rates and bioavailability will ensure the efficacious reinstatement of the once-powerful ancient synergy between light, water, and melatonin in a modern world.

A benzothiophene-quinoline-based targetable fluorescent chemosensor for detection of viscosity and mitochondrial imaging in live cells

Mitochondria are the sites of respiration in cells, and they participate in many indispensable biological processes. Because variations in mitochondrial viscosity can lead to dysfunctions of mitochondrial structure and function (and even induce malignant diseases), new sensors that can accurately monitor changes in mitochondrial viscosity are essential. To better investigate these changes, we report the development and evaluation of a novel benzothiophene-quinoline-based fluorescent chemosensor (BQL) that was designed especially for monitoring mitochondrial viscosity. BQL demonstrated a large Stokes shift (minimizing interference from autofluorescence) and a good response to viscosity (using the TICT principle). Moreover, BQL demonstrated little to no pH-dependency, polarity-dependency, or interference from other analytes. Thus, BQL has an excellent specificity for viscosity. BQL was used to monitor viscosity changes in mitochondria induced by ion carriers, and was used to report on viscosity in real time during mitophagy. To sum up, BQL provided a new approach for detecting viscosity in living cells and in vivo. BQL should prove to be an excellent tool for the analysis of viscosity changes in live cells.

Diminished α7 nicotinic acetylcholine receptor (α7nAChR) rescues amyloid-β induced atrial remodeling by oxi-CaMKII/MAPK/AP-1 axis-mediated mitochondrial oxidative stress

The potential coexistence of Alzheimer's disease (AD) and atrial fibrillation (AF) is increasingly common as aging-related diseases. However, little is known about mechanisms responsible for atrial remodeling in AD pathogenesis. α7 nicotinic acetylcholine receptors (α7nAChR) has been shown to have profound effects on mitochondrial oxidative stress in both organ diseases. Here, we investigate the role of α7nAChR in mediating the effects of amyloid-β (Aβ) in cultured mouse atrial cardiomyocytes (HL-1 cells) and AD model mice (APP/PS1). In vitro, apoptosis, oxidative stress and mitochondrial dysfunction induced by Aβ long-term (72h) in HL-1 cells were prevented by α-Bungarotoxin(α-BTX), an antagonist of α7nAChR. This cardioprotective effect was due to reinstating Ca²⁺ mishandling by decreasing the activation of CaMKII and MAPK signaling pathway, especially the oxidation of CaMKII (oxi-CaMKII). In vivo studies demonstrated that targeting knockdown of α7nAChR in cardiomyocytes could ameliorate AF progression in late-stage (12 months) APP/PS1 mice. Moreover, α7nAChR deficiency in cardiomyocytes attenuated APP/PS1-mutant induced atrial remodeling characterized by reducing fibrosis, atrial dilation, conduction dysfunction, and inflammatory mediator activities via suppressing oxi-CaMKII/MAPK/AP-1. Taken together, our findings suggest that diminished α7nAChR could rescue Aβ-induced atrial remodeling through oxi-CaMKII/MAPK/AP-1-mediated mitochondrial oxidative stress in atrial cells and AD mice.

Activity-Based Sensing for Chemistry-Enabled Biology: Illuminating Principles, Probes, and Prospects for Boronate Reagents for Studying Hydrogen Peroxide

Activity-based sensing (ABS) offers a general approach that exploits chemical reactivity as a method for selective detection and manipulation of biological analytes. Here, we illustrate the value of this chemical platform to enable new biological discovery through a case study in the design and application of ABS reagents for studying hydrogen peroxide (H2O2), a major type of reactive oxygen species (ROS) that regulates a diverse array of vital cellular signaling processes to sustain life. Specifically, we summarize advances in the use of activity-based boronate probes for the detection of H2O2 featuring high molecular selectivity over other ROS, with an emphasis on tailoring designs in chemical structure to promote new biological principles of redox signaling.

Linking the Amyloid, Tau, and Mitochondrial Hypotheses of Alzheimer's Disease and Identifying Promising Drug Targets

Damage or loss of brain cells and impaired neurochemistry, neurogenesis, and synaptic and nonsynaptic plasticity of the brain lead to dementia in neurodegenerative diseases, such as Alzheimer's disease (AD). Injury to synapses and neurons and accumulation of extracellular amyloid plaques and intracellular neurofibrillary tangles are considered the main morphological and neuropathological features of AD. Age, genetic and epigenetic factors, environmental stressors, and lifestyle contribute to the risk of AD onset and progression. These risk factors are associated with structural and functional changes in the brain, leading to cognitive decline. Biomarkers of AD reflect or cause specific changes in brain function, especially changes in pathways associated with neurotransmission, neuroinflammation, bioenergetics, apoptosis, and oxidative and nitrosative stress. Even in the initial stages, AD is associated with Aβ neurotoxicity, mitochondrial dysfunction, and tau neurotoxicity. The integrative amyloid-tau-mitochondrial hypothesis assumes that the primary cause of AD is the neurotoxicity of Aβ oligomers and tau oligomers, mitochondrial dysfunction, and their mutual synergy. For the development of new efficient AD drugs, targeting the elimination of neurotoxicity, mutual potentiation of effects, and unwanted protein interactions of risk factors and biomarkers (mainly Aβ oligomers, tau oligomers, and mitochondrial dysfunction) in the early stage of the disease seems promising.

Simultaneous Sensing of H2S and ATP with a Two-Photon Fluorescent Probe in Alzheimer's Disease: toward Understanding Why H2S Regulates Glutamate-Induced ATP Dysregulation

Energy deprivation and reduced levels of hydrogen sulfide (H₂S) in the brain is closely associated with Alzheimer's disease (AD). However, there is currently no fluorescent probe for precise exploration of both H₂S and adenosine triphosphate (ATP) to directly demonstrate their relationship and their dynamic pattern changes. Herein, we developed a two-photon fluorescent probe, named AD-3, to simultaneously image endogenous H₂S and ATP from two emission channels of fluorescent signals in live rat brains with AD. The probe achieved excellent selectivity and good detection linearity for H₂S in the 0-100 μM concentration range and ATP in the 2-5 mM concentration range, respectively, with a detection limit of 0.19 μM for H₂S and 0.01 mM for ATP. Fluorescence imaging in live cells reveals that such probe could successfully apply for simultaneous imaging and accurate quantification of H₂S and ATP in neuronal cells. Further using real-time quantitative polymerase chain reaction and Western blots, we confirmed that H₂S regulates ATP synthesis by acting on cytochrome C, cytochrome oxidase subunit 3 of complex IV, and protein 6 of complex I in the mitochondrial respiratory chain. Subsequently, we constructed a high-throughput screening platform based on AD-3 probe to rapidly screen the potential anti-AD drugs to control glutamate-stimulated oxidative stress associated with abnormal H₂S and ATP levels. Significantly, AD-3 probe was found capable of imaging of H₂S and ATP in APP/PS1 mice, and the concentration of H₂S and ATP in the AD mouse brain was found to be lower than that in wild-type mice.

Recent advances in nanotechnology mediated mitochondria-targeted imaging

Mitochondria play a critical role in cell growth and metabolism. And mitochondrial dysfunction is closely related to various diseases, such as cancers, and neurodegenerative and cardiovascular diseases. Therefore, it is of vital importance to monitor mitochondrial dynamics and function. One of the most widely used methods is to use nanotechnology-mediated mitochondria targeting and imaging. It has gained increasing attention in the past few years because of the flexibility, versatility and effectiveness of nanotechnology. In the past few years, researchers have implemented various types of design and construction of the mitochondrial structure dependent nanoprobes following assorted nanotechnology pathways. This review presents an overview on the recent development of mitochondrial structure dependent target imaging probes and classifies it into two main sections: mitochondrial membrane targeting and mitochondrial microenvironment targeting. Also, the significant impact of previous research as well as the application and perspectives will be demonstrated.

Lysosome-targeting benzothiazole-based fluorescent probe for imaging viscosity and hypochlorite levels in living cells and zebrafish

Viscosity and hypochlorite (OCl^-) play an important role in biological activities and may cause negative effects at abnormal levels. In this study, a novel lysosome-target fluorescent probe BDHA was obtained based on a benzothiazole derivative. Probe BDHA showed linear ranges of detection for viscosity from 1.62 cP to 851.6 cP with a fluorescent turn-on response. It can also be used as a sensor for OCl^- with a turn-off response and showed a good linear range from 0 to 390 μM, with the detection limit calculated to be 2.8 μM. Moreover, BDHA can also be used to image viscosity and OCl^- levels in HeLa cells and zebrafish, owing to its excellent optical properties.

Application of Fluorescent Probes in Reactive Oxygen Species Disease Model

Reactive oxygen species (ROS) play an important role in living activities as signaling molecules that regulate the living activities of organisms. There are many types of ROS, mainly including hydrogen peroxide (H2O2), hypochlorous acid (HOCl), hydroxyl radical (•OH), peroxyl radical (ROO•), singlet oxygen (1O2), peroxynitrite (ONOO-) and superoxide anion radical (O2-•) etc. Existing studies have shown that changes in ROS levels are closely associated with the development of many diseases, such as inflammation, cancer, cardiovascular disease, and neurodegenerative damage. Small molecule fluorescent probes have been widely used in biology, pathology and medical diagnosis due to their advantages of noninvasive, high sensitivity and in vivo real-time detection. It is extremely important to better apply small-molecule fluorescent probes to detect ROS levels in organisms to achieve early diagnosis of diseases and assessment of therapeutic conditions. This work focuses on summarizing the representative applications of some fluorescent probes in ROS disease models in recent years. This article focuses on summarizing the construction methods of various ROS-related disease models, and classifying and analyzing the basic ideas and methods of fluorescent probes applied to disease models according to the characteristics of various diseases.

A Novel fluorescent probe with large Stokes shift for the detection of viscosity changes and its imaging in living cells

As an important cellular micro environmental parameter, viscosity could reflect the status of living cells. Small molecular fluorescent probe is a vital tool to measure the change of viscosity in living cells. A novel fluorescence probe ZL-1 with a large Stokes shift (in methanol it reached to 153 nm and in glycerol it reached to 125 nm) and excellent sensitivity toward viscosity was developed. The sharp enhancement of the emission intensity for the probe ZL-1 from low viscous methanol to high viscous glycerol indicated the probe ZL-1 could be respond to the viscosity variations. Moreover, the probe ZL-1 has been successfully utilized to detect of viscosity variations in living cells.

Advances in Optical Imaging of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD), emerging as one of the most common chronic liver diseases including simple steatosis and non-alcoholic steatohepatitis (NASH), is likely to progress to liver fibrosis and hepatic carcinoma if not treated in time. Therefore, early diagnosis and treatment of NAFLD are necessary. Currently, liver biopsy, as the gold standard for clinical diagnosis of NAFLD, is not widely accepted by patients due to its invasiveness. However, other non-invasive methods that had been reported for NAFLD (such as magnetic resonance imaging, positron emission tomography, and ultrasound) still suffer from low resolution and sensitivity, which are available as a guide for liver biopsy sometimes. As a non-invasive modality with high spatiotemporal resolution and superior sensitivity, optical imaging methods have been widely favored in recent years, mainly including fluorescence imaging, photoacoustic imaging, and bioluminescence imaging. With these optical imaging approaches, a series of optical probes based on optical and molecular-specific design have been developed for the biomarker diagnosis and research of diseases. In this review, we summarize the existing non-invasive optical imaging probes for the detection of biomarkers in NAFLD, including microenvironment (viscosity, polarity), ROS, RSS, ions, proteins, and nucleic acids. Design strategies for optical imaging probes and their applications in NAFLD bioimaging are discussed and focused on. We also highlight the potential challenges and prospects of designing new generations of optical imaging probes in NAFLD studies, which will further enhance the diversity, practicality, and clinical feasibility of NAFLD research.

Mitochondrial-Targeting Near-Infrared Fluorescent Probe for Visualizing Viscosity in Drug-Induced Cells and a Fatty Liver Mouse Model

Mitochondria, as "cell energy stations", are involved in the regulation of various cell functions. Recent investigations revealed that mitochondrial dysfunction that can cause an intracellular viscosity mutation, a process that is associated with an increasing number of diseases that are not curable or manageable. However, conventional viscometers cannot be used to monitor the viscosity changes in living cells and in vivo. In order to cater to the complex biological environment, we present a chemical toolbox, MI-BP-CC, that employs N,N-diethyl and double bonds as sensitive sites for viscosity based on the TICT mechanism (twisted intramolecular charge transfer) to monitor the viscosity of living cells and fatter liver mice. MI-BP-CC features good mitochondrial targeting and a near-infrared emission. Surprisingly, in the presence of viscosity, the MI-BP-CC probe exhibited an ultrasensitive model for viscosity detection showing a red fluorescence signal from a silent "off" state to "on". More importantly, utilizing the satisfactory detection performance of MI-BP-CC, we have successfully visualized increased viscosity under the pathological models of Parkinson's (PD) and fatty liver mice. We anticipate that these findings will provide a convenient and efficient tool to understand physiological functions of viscosity in more biosystems.

Beta-Amyloid Instigates Dysfunction of Mitochondria in Cardiac Cells

Alzheimer’s disease (AD) includes the formation of extracellular deposits comprising aggregated β-amyloid (Aβ) fibers associated with oxidative stress, inflammation, mitochondrial abnormalities, and neuronal loss. There is an associative link between AD and cardiac diseases; however, the mechanisms underlying the potential role of AD, particularly Aβ in cardiac cells, remain unknown. Here, we investigated the role of mitochondria in mediating the effects of Aβ_1-40 and Aβ_1-42 in cultured cardiomyocytes and primary coronary endothelial cells. Our results demonstrated that Aβ_1-40 and Aβ_1-42 are differently accumulated in cardiomyocytes and coronary endothelial cells. Aβ_1-42 had more adverse effects than Aβ_1-40 on cell viability and mitochondrial function in both types of cells. Mitochondrial and cellular ROS were significantly increased, whereas mitochondrial membrane potential and calcium retention capacity decreased in both types of cells in response to Aβ_1-42. Mitochondrial dysfunction induced by Aβ was associated with apoptosis of the cells. The effects of Aβ_1-42 on mitochondria and cell death were more evident in coronary endothelial cells. In addition, Aβ_1-40 and Aβ_1-42 significantly increased Ca²⁺ -induced swelling in mitochondria isolated from the intact rat hearts. In conclusion, this study demonstrates the toxic effects of Aβ on cell survival and mitochondria function in cardiac cells.

Investigation of apoptosis based on fluorescence lifetime imaging microscopy with a mitochondria-targeted viscosity probe

Cell apoptosis detection based on the functionality changes of cellular organelles, such as mitochondria, offers a quantitative method compared to morphology-based detection. However, the conventional detection methods for potential variation of the mitochondrial membrane based on fluorescence spectrum changes cannot offer a precise quantification of the degree of apoptosis. Here, a mitochondria-targeted two-photon viscosity probe (TPA-Mit), which sensitively responds to viscosity variations with fluorescence lifetime changes, is designed to detect the viscosity of mitochondria. Noteworthily, the proposed phasor fluorescence lifetime imaging microscopy (phasor-FLIM) allows for more precise quantification (in terms of smaller uncertainty) when estimating the degree of apoptosis with a microviscosity probe. The experimental results of SKOV-3 cells show that the fluorescence lifetime of mitochondria-targeted TPA-Mit increased from 550 ps to 800 ps after 24 hours of paclitaxel (PTX)-induced apoptosis. We believe that our method provides a new means for the measurement of cellular microviscosity and apoptosis monitoring at early stages.

Here we designed a mitochondria-targeted two-photon viscosity probe (TPA-Mit), which sensitively responds to viscosity variations with fluorescence lifetime changes.

A simple dual-response fluorescent probe for imaging of viscosity and ONOO- through different fluorescence signals in living cells and zebrafish

Cellular viscosity is a prominent micro-environmental parameter and peroxynitrite is an essential reactive oxygen special, both of which are involved in various pathological and physiological processes. When the intracellular viscosity is abnormal or the ONOO^- concentration is irregular, the normal function of cells will be disturbed. Herein, we rationally designed and synthesized a novel multichannel fluorescent probe (probe 1) for multichannel imaging of viscosity and peroxynitrite. Probe 1 displayed about 108-fold enhancement as the viscosity increased from 1.005 cP to 1090 cP. Moreover, the fluorescence intensity at 540 nm was quickly increased after adding ONOO^-. It should be noted that probe 1 has high sensitivity, selectivity and low cytotoxicity, which can be successfully employed for the visualization of exogenous and endogenous ONOO^- and imaging viscosity changes in HeLa cells by different fluorescent signals. Furthermore, probe 1 could monitor the change of ONOO^- induced by LPS (lipopolysaccharide) and IFN-γ (interferon-γ) in zebrafish. This result reveals that probe 1 may inspire more diagnostic and therapeutic programs for viscosity-peroxynitrite related diseases shortly.

Olaparib Is a Mitochondrial Complex I Inhibitor That Kills Temozolomide-Resistant Human Glioblastoma Cells

Glioblastoma represents the highest grade of brain tumors. Despite maximal resection surgery associated with radiotherapy and concomitant followed by adjuvant chemotherapy with temozolomide (TMZ), patients have a very poor prognosis due to the rapid recurrence and the acquisition of resistance to TMZ. Here, initially considering that TMZ is a prodrug whose activation is pH-dependent, we explored the contribution of glioblastoma cell metabolism to TMZ resistance. Using isogenic TMZ-sensitive and TMZ-resistant human glioblastoma cells, we report that the expression of O6-methylguanine DNA methyltransferase (MGMT), which is known to repair TMZ-induced DNA methylation, does not primarily account for TMZ resistance. Rather, fitter mitochondria in TMZ-resistant glioblastoma cells are a direct cause of chemoresistance that can be targeted by inhibiting oxidative phosphorylation and/or autophagy/mitophagy. Unexpectedly, we found that PARP inhibitor olaparib, but not talazoparib, is also a mitochondrial Complex I inhibitor. Hence, we propose that the anticancer activities of olaparib in glioblastoma and other cancer types combine DNA repair inhibition and impairment of cancer cell respiration.

Small molecule based fluorescent chemosensors for imaging the microenvironment within specific cellular regions

The microenvironment (local environment), including viscosity, temperature, polarity, hypoxia, and acidic-basic status (pH), plays indispensable roles in cellular processes. Significantly, organelles require an appropriate microenvironment to perform their specific physiological functions, and disruption of the microenvironmental homeostasis could lead to malfunctions of organelles, resulting in disorder and disease development. Consequently, monitoring the microenvironment within specific organelles is vital to understand organelle-related physiopathology. Over the past few years, many fluorescent probes have been developed to help reveal variations in the microenvironment within specific cellular regions. Given that a comprehensive understanding of the microenvironment in a particular cellular region is of great significance for further exploration of life events, a thorough summary of this topic is urgently required. However, there has not been a comprehensive and critical review published recently on small-molecule fluorescent chemosensors for the cellular microenvironment. With this review, we summarize the recent progress since 2015 towards small-molecule based fluorescent probes for imaging the microenvironment within specific cellular regions, including the mitochondria, lysosomes, lipid drops, endoplasmic reticulum, golgi, nucleus, cytoplasmic matrix and cell membrane. Further classifications at the suborganelle level, according to detection of microenvironmental factors by probes, including polarity, viscosity, temperature, pH and hypoxia, are presented. Notably, in each category, design principles, chemical synthesis, recognition mechanism, fluorescent signals, and bio-imaging applications are summarized and compared. In addition, the limitations of the current microenvironment-sensitive probes are analyzed and the prospects for future developments are outlined. In a nutshell, this review comprehensively summarizes and highlights recent progress towards small molecule based fluorescent probes for sensing and imaging the microenvironment within specific cellular regions since 2015. We anticipate that this summary will facilitate a deeper understanding of the topic and encourage research directed towards the development of probes for the detection of cellular microenvironments.

Screening of dicyanoisophorone-based probes for highly sensitive detection of viscosity changes in living cells and zebrafish

Herein, seven viscosity-sensitive probes were developed via simple structural modification of dicyanoisophorone (DCO)-derived dyes. Among them, DCO-5 significantly enhances (180-fold) the response signal in highly viscous aqueous media while showing insensitivity to polarity changes or pH variations, and enables the successful detection of viscosity changes in nystatin-treated HepG2 cells, PC 12 cells and zebrafish.

A "double-locked" probe for the detection of hydrogen sulfide in a viscous system

A novel "double-locked" probe, DCO-H2S-V, was prepared for detecting hydrogen sulfide in a highly viscous system. Experiments demonstrated that only when H2S and a high viscosity environment coexist in a cell, can the probe be activated effectively and emit fluorescence. This has been successfully used for detecting the changes in viscosity and H2S in a Parkinson's disease model, PC-12 cells treated with glutamate.

Real-time imaging of viscosity in the mitochondrial matrix by a red-emissive molecular rotor

Mitochondrial matrix contains numerous metabolism-related proteins/enzymes and nucleic acids, which play key roles in the process of energy generation and signal transduction. The fluctuations in mitochondrial biomacromolecular levels lead to the changes in the mitochondrial matrix viscosity; therefore, real-time measuring the mitochondrial matrix viscosity is of great significance for the in-depth understanding of the mitochondrial physiology and pathobiology. However, investigations are limited due to the lack of a mitochondrial matrix-specific molecular rotor. Herein, we report a design of a molecular rotor that is specifically enriched in the mitochondrial matrix. The red fluorescence of the rotor switches on when the viscosity increases, enabling the real-time monitoring of the viscosity change therein. Interestingly, the rotor showed non-fluorescence behaviour in the liposome (mimicking membrane structure), avoiding fluorescence interference from the mitochondrial bilayer membrane. Super-resolution imaging reveals that the viscosity is uneven in an individual mitochondrion.

A Mitochondrial-Targeting Near-Infrared Fluorescent Probe for Revealing the Effects of Hydrogen Peroxide And Heavy Metal Ions on Viscosity

As an important cell organelle, the mitochondrion has special viscosities, while abnormal mitochondrial viscosity is closely related to many diseases. Hydrogen peroxide (H₂O₂) is an active molecule related to the cell microenvironment, and its influence on mitochondrial viscosity is still not clear, so further investigation is needed. In addition, since excessive accumulation of heavy metal ions would lead to cells' dysfunction, the study of effect of excessive heavy metal ions on mitochondrial viscosity has not been reported. Herein, we designed and synthesized a mitochondrial-targeting near-infrared fluorescent probe (Mito-NV) for real-time in situ imaging and analysis of mitochondrial viscosity. Furthermore, the probe revealed that H₂O₂ can raise mitochondrial viscosity, while heavy metal ions reduce the viscosity. This work is of great significance for understanding the execution of mitochondrial functions and the occurrence and development of related diseases.

Monitoring of the decreased mitochondrial viscosity during heat stroke with a mitochondrial AIE probe

Heat stroke is a fatal condition which usually results in central nervous system dysfunction, organism damage and even death. The relationship between heat stroke and mitochondria is still relatively unknown due to a lack of suitable tools. Herein, an aggregation-induced emission (AIE) probe CSP, by introducing a pyridinium cation as the mitochondria-targeted group to an AIE active core cyanostilbene skeleton, is highly sensitive to viscosity changes due to the restriction of intramolecular motion (RIM) and inhibition of twisted intramolecular charge transfer (TICT) in high-viscosity systems. As expected, with the viscosity increasing from 0.903 cP (0% glycerol) to 965 cP (99% glycerol), CSP exhibited a significant enhancement (more than 117-fold) in fluorescence intensity at 625 nm, with an excellent linear relationship between log I _{625 nm} and log η (R² = 0.9869, slope as high as 0.6727). More importantly, using CSP we have successfully monitored the decreased mitochondrial viscosity during heat stroke for the first time. All these features render the probe a promising candidate for further understanding the mechanism underlying mitochondria-associated heat stroke.

Systematic review and meta-analysis on the role of mitochondrial cytochrome c oxidase in Alzheimer's disease

OBJECTIVE

The present study was designed to test the hypothesis that there is a reduction in the activity of the enzyme cytochrome c oxidase (Cox) in Alzheimer's disease (AD).

METHODS

Systematic review of literature and meta-analysis were used with data obtained from the PubMed, Scopus, MEDLINE, Lilacs, Eric and Cochrane. The keywords were Alzheimer's AND Cox AND mitochondria; Alzheimer's AND Cox AND mitochondria; Alzheimer's AND complex IV AND mitochondria. A total of 1372 articles were found, 23 of them fitting the inclusion criteria. The data were assembled in an Excel spreadsheet and analysed using the RevMan software. A random effects model was adopted to the estimative of the effect.

RESULTS

The data shows a significant decrease in the activity of the Cox AD patients and animal models.

CONCLUSION

Cox enzyme may be an important molecular component involved in the mechanisms underlying AD. Therefore, this enzyme may represent a possible new biomarker for the disease as a complementary diagnosis and a new treatment target for AD.

Mitochondrial Regulation of Microglial Immunometabolism in Alzheimer's Disease

Alzheimer’s disease (AD) is an age-associated terminal neurodegenerative disease with no effective treatments. Dysfunction of innate immunity is implicated in the pathogenesis of AD, with genetic studies supporting a causative role in the disease. Microglia, the effector cells of innate immunity in the brain, are highly plastic and perform a diverse range of specialist functions in AD, including phagocytosing and removing toxic aggregates of beta amyloid and tau that drive neurodegeneration. These immune functions require high energy demand, which is regulated by mitochondria. Reflecting this, microglia have been shown to be highly metabolically flexible, reprogramming their mitochondrial function upon inflammatory activation to meet their energy demands. However, AD-associated genetic risk factors and pathology impair microglial metabolic programming, and metabolic derailment has been shown to cause innate immune dysfunction in AD. These findings suggest that immunity and metabolic function are intricately linked processes, and targeting microglial metabolism offers a window of opportunity for therapeutic treatment of AD. Here, we review evidence for the role of metabolic programming in inflammatory functions in AD, and discuss mitochondrial-targeted immunotherapeutics for treatment of the disease.

Targeting the Mitochondrial Permeability Transition Pore to Prevent Age-Associated Cell Damage and Neurodegeneration

The aging process is associated with significant alterations in mitochondrial function. These changes in mitochondrial function are thought to involve increased production of reactive oxygen species (ROS), which over time contribute to cell death, senescence, tissue degeneration, and impaired tissue repair. The mitochondrial permeability transition pore (mPTP) is likely to play a critical role in these processes, as increased ROS activates mPTP opening, which further increases ROS production. Injury and inflammation are also thought to increase mPTP opening, and chronic, low-grade inflammation is a hallmark of aging. Nicotinamide adenine dinucleotide (NAD+) can suppress the frequency and duration of mPTP opening; however, NAD+ levels are known to decline with age, further stimulating mPTP opening and increasing ROS release. Research on neurodegenerative diseases, particularly on Parkinson's disease (PD) and Alzheimer's disease (AD), has uncovered significant findings regarding mPTP openings and aging. Parkinson's disease is associated with a reduction in mitochondrial complex I activity and increased oxidative damage of DNA, both of which are linked to mPTP opening and subsequent ROS release. Similarly, AD is associated with increased mPTP openings, as evidenced by amyloid-beta (Aβ) interaction with the pore regulator cyclophilin D (CypD). Targeted therapies that can reduce the frequency and duration of mPTP opening may therefore have the potential to prevent age-related declines in cell and tissue function in various systems including the central nervous system.

Loss of function of the mitochondrial peptidase PITRM1 induces proteotoxic stress and Alzheimer's disease-like pathology in human cerebral organoids

Mutations in pitrilysin metallopeptidase 1 (PITRM1), a mitochondrial protease involved in mitochondrial precursor processing and degradation, result in a slow-progressing syndrome characterized by cerebellar ataxia, psychotic episodes, and obsessive behavior, as well as cognitive decline. To investigate the pathogenetic mechanisms of mitochondrial presequence processing, we employed cortical neurons and cerebral organoids generated from PITRM1-knockout human induced pluripotent stem cells (iPSCs). PITRM1 deficiency strongly induced mitochondrial unfolded protein response (UPR^mt) and enhanced mitochondrial clearance in iPSC-derived neurons. Furthermore, we observed increased levels of amyloid precursor protein and amyloid β in PITRM1-knockout neurons. However, neither cell death nor protein aggregates were observed in 2D iPSC-derived cortical neuronal cultures. On the other hand, over time, cerebral organoids generated from PITRM1-knockout iPSCs spontaneously developed pathological features of Alzheimer's disease (AD), including the accumulation of protein aggregates, tau pathology, and neuronal cell death. Single-cell RNA sequencing revealed a perturbation of mitochondrial function in all cell types in PITRM1-knockout cerebral organoids, whereas immune transcriptional signatures were substantially dysregulated in astrocytes. Importantly, we provide evidence of a protective role of UPR^mt and mitochondrial clearance against impaired mitochondrial presequence processing and proteotoxic stress. Here, we propose a novel concept of PITRM1-linked neurological syndrome whereby defects of mitochondrial presequence processing induce an early activation of UPR^mt that, in turn, modulates cytosolic quality control pathways. Thus, our work supports a mechanistic link between mitochondrial function and common neurodegenerative proteinopathies.

Fluorescent Diagnostic Probes in Neurodegenerative Diseases

Neurodegenerative diseases are debilitating disorders that feature progressive and selective loss of function or structure of anatomically or physiologically associated neuronal systems. Both chronic and acute neurodegenerative diseases are associated with high morbidity and mortality along with the death of neurons in different areas of the brain; moreover, there are few or no effective curative therapy options for treating these disorders. There is an urgent need to diagnose neurodegenerative disease as early as possible, and to distinguish between different disorders with overlapping symptoms that will help to decide the best clinical treatment. Recently, in neurodegenerative disease research, fluorescent-probe-mediated biomarker visualization techniques have been gaining increasing attention for the early diagnosis of neurodegenerative diseases. A survey of fluorescent probes for sensing and imaging biomarkers of neurodegenerative diseases is provided. These imaging probes are categorized based on the different potential biomarkers of various neurodegenerative diseases, and their advantages and disadvantages are discussed. Guides to develop new sensing strategies, recognition mechanisms, as well as the ideal features to further improve neurodegenerative disease fluorescence imaging are also explored.

Common aspects between glaucoma and brain neurodegeneration

Neurodegeneration can be defined as progressive cell damage to nervous system cells, and more specifically to neurons, which involves morphologic alterations and progressive loss of function until cell death. Glaucoma exhibits many aspects of neurodegenerative disease. This review examines the pathogenesis of glaucoma, comparing it with that of Alzheimer's disease (AD) and Parkinson's disease (PD), highlighting their common features. Indeed, in all three diseases there are not only the same types of pathogenic events, but also similarities of temporal cadences that determine neuronal damage. All three age-related illnesses have oxidative damage and mitochondrial dysfunction as the first pathogenic steps. The consequence of these alterations is the death of visual neurons in glaucoma, cognitive neurons in AD and regulatory motor neurons (substantia nigra) in PD. The study of these common pathogenic events (oxidative stress, mitochondrial dysfunction, protein degradation, apoptosis and autophagy) leads us to consider common therapeutic strategies for the treatment and prevention of these diseases. Also, examination of the genetic aspects of the pathways involved in neurodegenerative processes plays a key role in shedding light on the details of pathogenesis and can suggest new treatments. This review discusses the common molecular aspects involved in these three oxidative-stress and age-related diseases.

Promising Molecular Targets for Pharmacological Therapy of Neurodegenerative Pathologies

Drug development for the treatment of neurodegenerative diseases has to confront numerous problems occurring, in particular, because of attempts to address only one of the causes of the pathogenesis of neurological disorders. Recent advances in multitarget therapy research are gaining momentum by utilizing pharmacophores that simultaneously affect different pathological pathways in the neurodegeneration process. The application of such a therapeutic strategy not only involves the treatment of symptoms, but also mainly addresses prevention of the fundamental pathological processes of neurodegenerative diseases and the reduction of cognitive abilities. Neuroinflammation and oxidative stress, mitochondrial dysfunction, dysregulation of the expression of histone deacetylases, and aggregation of pathogenic forms of proteins are among the most common and significant pathological features of neurodegenerative diseases. In this review, we focus on the molecular mechanisms and highlight the main aspects, including reactive oxygen species, the cell endogenous antioxidant system, neuroinflammation triggers, metalloproteinases, α-synuclein, tau proteins, neuromelanin, histone deacetylases, presenilins, etc. The processes and molecular targets discussed in this review could serve as a starting point for screening leader compounds that could help prevent or slow down the development of neurodegenerative diseases.

Physical exercise during exposure to 40-Hz light flicker improves cognitive functions in the 3xTg mouse model of Alzheimer's disease

BACKGROUND

Exercise promotes brain health and improves cognitive functioning in the elderly, while 40-Hz light flickering through the visual cortex reduces amyloid beta (Aβ) by stabilizing gamma oscillation. We examined whether exercise was associated with hippocampus-mediated improvement in cognitive functioning in the 3xTg-Alzheimer's disease (3xTg-AD) murine model following exposure to 40-Hz light flickering and exercise.

METHODS

We subjected 12-month-old 3xTg-AD mice to exercise and 40-Hz light flickering for 3 months to investigate spatial learning, memory, long-term memory, Aβ levels, tau levels, mitochondrial functioning including Ca2+ retention and H2O2 emission, apoptosis, and neurogenesis in the hippocampus.

RESULTS

Treatments had a positive effect; however, the combination of exercise and 40-Hz light flickering exposure was most effective in reducing Aβ and tau levels. Reducing Aβ and tau levels by combination of exercise and 40-Hz light flickering improves Ca2+ homeostasis and reactive oxygen species such as H2O2 in mitochondria and apoptosis including bax, bcl-2, cytochrome c, and cleaved caspase-3 and cell death, cell differentiation, and neurogenesis in the 3xTg-AD model of the hippocampus, resulting in improving cognitive impairment such as spatial learning, memory and long term memory.

CONCLUSION

Our results show that exercising in a 40-Hz light flickering environment may improve cognitive functioning by reducing Aβ and tau levels, thereby enhancing mitochondrial function and neuroplasticity.

A novel carbazolyl GFP chromophore analogue: synthesis strategy and acidic pH-activatable lysosomal probe for tracing endogenous viscosity changes

A novel, acidic pH-activatable carbazolyl GFP chromophore analogue was designed for tracing lysosomal viscosity changes.

Simultaneous imaging of mitochondrial viscosity and hydrogen peroxide in Alzheimer's disease by a single near-infrared fluorescent probe with a large Stokes shift

Simultaneous imaging of mitochondrial viscosity and hydrogen peroxide in Alzheimer's disease by a single near-infrared fluorescent probe with a large Stokes shift.