Elevated protein tyrosine phosphatase activity and increased membrane viscosity are associated with impaired activation of the insulin receptor kinase in old rats

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.

Molecular profiling of high-level athlete skeletal muscle after acute endurance or resistance exercise - A systems biology approach

OBJECTIVE

Long-term high-level exercise training leads to improvements in physical performance and multi-tissue adaptation following changes in molecular pathways. While skeletal muscle baseline differences between exercise-trained and untrained individuals have been previously investigated, it remains unclear how training history influences human multi-omics responses to acute exercise.

METHODS

We recruited and extensively characterized 24 individuals categorized as endurance athletes with >15 years of training history, strength athletes or control subjects. Timeseries skeletal muscle biopsies were taken from M. vastus lateralis at three time-points after endurance or resistance exercise was performed and multi-omics molecular analysis performed.

RESULTS

Our analyses revealed distinct activation differences of molecular processes such as fatty- and amino acid metabolism and transcription factors such as HIF1A and the MYF-family. We show that endurance athletes have an increased abundance of carnitine-derivates while strength athletes increase specific phospholipid metabolites compared to control subjects. Additionally, for the first time, we show the metabolite sorbitol to be substantially increased with acute exercise. On transcriptional level, we show that acute resistance exercise stimulates more gene expression than acute endurance exercise. This follows a specific pattern, with endurance athletes uniquely down-regulating pathways related to mitochondria, translation and ribosomes. Finally, both forms of exercise training specialize in diverging transcriptional directions, differentiating themselves from the transcriptome of the untrained control group.

CONCLUSIONS

We identify a "transcriptional specialization effect" by transcriptional narrowing and intensification, and molecular specialization effects on metabolomic level Additionally, we performed multi-omics network and cluster analysis, providing a novel resource of skeletal muscle transcriptomic and metabolomic profiling in highly trained and untrained individuals.

Organic Fluorescent Probes for Monitoring Micro-Environments in Living Cells and Tissues

As a vital parameter in living cells and tissues, the micro-environment is crucial for the living organisms. Significantly, organelles require proper micro-environment to achieve normal physiological processes, and the micro-environment in organelles can reflect the state of organelles in living cells. Moreover, some abnormal micro-environments in organelles are closely related to organelle dysfunction and disease development. So, visualizing and monitoring the variation of micro-environments in organelles is helpful for physiologists and pathologists to study the mechanisms of the relative diseases. Recently, a large variety of fluorescent probes was developed to study the micro-environments in living cells and tissues. However, the systematic and comprehensive reviews on the organelle micro-environment in living cells and tissues have rarely been published, which may hinder the research progress in the field of organic fluorescent probes. In this review, we will summarize the organic fluorescent probes for monitoring the microenvironment, such as viscosity, pH values, polarity, and temperature. Further, diverse organelles (mitochondria, lysosome, endoplasmic reticulum, cell membrane) about microenvironments will be displayed. In this process, the fluorescent probes about the "off-on" and ratiometric category (the diverse fluorescence emission) will be discussed. Moreover, the molecular designing, chemical synthesis, fluorescent mechanism, and the bio-applications of these organic fluorescent probes in cells and tissues will also be discussed. Significantly, the merits and defects of current microenvironment-sensitive probes are outlined and discussed, and the development tendency and challenges for this kind of probe are presented. In brief, this review mainly summarizes some typical examples and highlights the progress of organic fluorescent probes for monitoring micro-environments in living cells and tissues in recent research. We anticipate that this review will deepen the understanding of microenvironment in cells and tissues and facilitate the studies and development of physiology and pathology.

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.

Phosphorescent Ir(III) Complexes for Biolabeling and Biosensing

Cyclometalated Ir(III) complexes exhibit strong phosphorescence emission with lifetime of submicroseconds to several microseconds at room temperature. Their synthetic versatility enables broad control of physical properties, such as charge and lipophilicity, as well as emission colors. These favorable properties have motivated the use of Ir(III) complexes in luminescent bioimaging applications. This review examines the recent progress in the development of phosphorescent biolabels and sensors based on Ir(III) complexes. It begins with a brief introduction about the basic principles of the syntheses and photophysical processes of cyclometalated Ir(III) complexes. Focus is placed on illustrating the broad imaging utility of Ir(III) complexes. Phosphorescent labels illuminating intracellular organelles, including mitochondria, lysosomes, and cell membranes, are summarized. Ir(III) complexes capable of visualization of tumor spheroids and parasites are also introduced. Facile chemical modification of the cyclometalating ligands endows the Ir(III) complexes with strong sensing ability. Sensors of temperature, pH, CO₂, metal ions, anions, biosulfur species, reactive oxygen species, peptides, and viscosity have recently been added to the molecular imaging tools. This diverse utility demonstrates the potential of phosphorescent Ir(III) complexes toward bioimaging applications.

Modulating insulin signaling and trafficking at the blood-brain barrier endothelium using lipid based nanoemulsions

The compositionally distinct lipid rafts present in the plasma membrane regulate the restrictive trafficking and signal transduction in the blood-brain barrier (BBB) endothelium. Several metabolic and neurodegenerative diseases are associated with lipid homeostasis disruption within the BBB endothelium. Here, we hypothesized that the delivery of lipid triglyceride based nanoemulsions containing unsaturated fatty acids (UFAs) provides a novel non-pharmacological approach to modulate lipid raft integrity and rectify the aberrant trafficking and signal transduction. The current study has shown that soybean oil nanoemulsions (SNEs) altered the morphology of lipid rafts that are stained by Alex Fluor 647 labelled cholera toxin (AF647-CTX) in polarized human cerebral microvascular endothelial (hCMEC/D3) cell monolayers. Moreover, western blot and flow cytometry analysis showed that SNEs containing polyunsaturated fatty acids (PUFAs) increased phospo-AKT (p-AKT) expression, a marker for the stimulation of metabolic arm of insulin signaling, and insulin uptake in hCMEC/D3 monolayers. However, olive oil nanoemulsions (ONEs) containing monounsaturated fatty acids (MUFAs) had no detectable impact on lipid raft integrity, AKT phosphorylation, or insulin uptake. These findings provided direct evidence that SNEs containing PUFAs can upregulate insulin-pAKT pathway, facilitate insulin trafficking at the BBB, and potentially address cerebrovascular dysfunction in metabolic and neurodegenerative diseases.

Exploring BODIPY-Based Sensor for Imaging of Intracellular Microviscosity in Human Breast Cancer Cells

BODIPY-based molecular rotors are highly attractive imaging tools for imaging intracellular microviscosity in living cells. In our study, we investigated the ability to detect the microviscosity of biological objects by using BDP-NO₂ and BDP-H molecular rotors. We describe in detail the optical properties of BDP-NO₂ and BDP-H molecular rotors in aqueous media with and without proteins, together with their accumulation dynamics and localization in live and fixed human breast cancer cells. Furthermore, we investigate the applicability of these molecules to monitor microviscosity in the organelles of human breast cancer cells by fluorescence lifetime imaging microscopy (FLIM). We demonstrate that the BDP-NO₂ molecular rotor aggregates in aqueous media and is incompatible with live cell imaging. The opposite effect is observed with BDP-H which preserves its stability in aqueous media, diffuses through the plasma membrane and accumulates in lipid droplets (LDs) and the cytosol of both live and fixed MCF-7 and MDA-MB-231 cancer cells. Finally, by utilizing BDP-H we demonstrate that LD microviscosity is significantly elevated in more malignant MDA-MB-231 human breast cancer cells, as compared to MCF-7 breast cancer cells. Our findings demonstrate that BDP-H is a water-compatible probe that can be successfully applied to measure microviscosity in the LDs of living cells.

A dual-response fluorescent probe for N2H4 and viscosity in living cells and zebrafish to evaluate liver injury

Hydrazide drugs can cause severe drug-induced liver injury owing to the enzymatic release of N₂H₄ in the liver. Also, changes in cellular viscosity are associated with liver damage. Thus, simultaneous monitoring of changes in N₂H₄ levels and viscosity can be used to evaluate the side effects of hydrazide drugs. Herein, we firstly reported a near-infrared fluorescent probe (FNN), which contains 1,8-naphthalimide as the fluorophore and a chalcone moiety as the responsive receptor, for sensitively detecting intracellular viscosity and N₂H₄. FNN showed a fast 'turn-on' fluorescence response to N₂H₄ with excellent selectivity. Additionally, FNN could selectively track viscosity without interference from polarity, pH, and other active species. Furthermore, imaging experiments suggested that FNN could be successfully applied in living cells and zebrafish larvae and embryos, which is of great importance for effectively assessing the degree of liver injury.

Imaging and Detection of Hepatocellular Carcinoma with a Hepatocyte-Specific Fluorescent Probe

Hepatocellular carcinoma is a highly invasive malignant tumor of the liver, which is the main cause of cancer-related death. The cancerization of hepatocytes may lead to the changes of cell microenvironment, active substances, and enzymes. Viscosity is one of the important parameters of cell microenvironment. Therefore, the study of the change in the viscosity of hepatocytes is very important for the detection and treatment of liver cancer. However, the hepatocyte-specific fluorescent probes which can detect viscosity have not been developed yet. Herein, the first hepatocyte-specific fluorescent probe (HT-V) for viscosity detection was designed and synthesized, which exhibited excellent optical properties for biological imaging studies. By using the unique probe HT-V, compared with the normal liver cells, a significant increase of viscosity in the liver cancer cells was observed in the cell imaging experiment. The organ imaging experiments showed that the probe HT-V could be successfully used to diagnose and image hepatocellular carcinoma in vivo. In addition, in situ imaging revealed that the new probe HT-V can specifically target and image hepatocellular carcinoma in mice. We expected that this powerful tool may provide guidance for the detection and imaging of hepatocellular carcinoma in the future.

p-Aminostyryl thiazole orange derivatives for monitoring mitochondrial viscosity in live cells

Viscosity of cell microenvironment plays a significant role in maintaining the normal life activities of cells. Particularly, the abnormal viscosity in mitochondria is closely associated with lots of diseases and cellular dysfunctions. Herein, we developed a group of p-aminostyryl thiazole orange derivatives with different amino side chains. These probes showed good fluorescence response to viscosity with twisted intramolecular charge transfer mechanism, among them, the probes with diethylamino (TOB), dibutylamino (TOC) and pyrrolidin (TOE) side chains showed better response to the viscosity with 78-fold, 55-fold, and 88-fold fluorescence enhancement in 95% glycerol solution respectively. TOB, TOC, and TOE could enter live cells and mainly located in mitochondria. Treatment HeLa cells with nystatin, lipopolysaccharide or oleic acid caused significant fluorescence enhancement of these probes, suggesting the good potential for monitoring the variation of mitochondrial viscosity, as well as for investigating the related physiological process of inflammation and lipid metabolism.

A porphyrin-triazatruxene dyad for ratiometric two-photon fluorescent sensing of intracellular viscosity

By combining an electron-rich triazatruxene unit (TAT) to an electron-deficient zinc porphyrin fluorophore (ZnPor) via an ethynyl bridge, a new two-photon fluorescent viscosity rotor (TAT-ZnPor) with typical donor-π-acceptor (D-π-A) electronic...

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.

Mechanistic and therapeutic insight into the effects of cinnamon in polycystic ovary syndrome: a systematic review

Polycystic ovary syndrome (PCOS) is one of the most common endocrine diseases in the women at their reproductive age. Nowadays, the use of herbal compounds for lesser side effects, as compared to drug treatments, has become popular for the prevention and reduction of the complications of this disease. Evidence suggests that cinnamon, given its antioxidant and anti-inflammatory properties, can be associated with reduced metabolic complications from chronic non-communicable diseases. This systematic review aimed to determine the potential effect of cinnamon on the metabolic status in the PCOS. PICO framework for current systematic review was Population (P): subjects with PCOS; Intervention (I): oral cinnamon supplement; Comparison (C): the group as control or administered placebo; and Outcome (O): changed inflammatory, oxidative stress, lipid profile, glycemic, hormonal and anthropometric parameters and ovarian function. PubMed, Scopus, EMBASE, ProQuest and Google Scholar were searched from their very inception until January, 2020, considering specific keywords to explore the related studies. Out of 266 studies retrieved by the search strategy, only nine were eligible for evaluation. All clinical trials, animal studies, and published English-language journal studies were eligible for this review. The results showed that increased high-density lipoprotein and insulin sensitivity were increased by the cinnamon supplementation while low-density lipoprotein, triglyceride, and blood glucose were decreased in patients with PCOS. However, the results related to the potential effects of cinnamon on body weight and body mass index were inconsistent, thus calling for further studies. Also, despite improved results regarding the effect of cinnamon on oxidative stress and ovarian function, further studies are required to explore the precise mechanisms. Overall, the effects of cinnamon on the improvement of metabolic status in PCOS were promising. However, to observe clinical changes following cinnamon supplementation in PCOS, more clinical trials with higher doses of cinnamon and a longer duration of intervention are needed.

A novel mitochondrial-targeting fluorescent probe based on 1,4-dihydropyridine to visualize and monitor the viscosity of live cells and mice in vivo

Cell viscosity is related to some diseases, such as diabetes, atherosclerosis, and Alzheimer's disease. These diseases can cause abnormal viscosity of the cell mitochondrial matrix. 1,4-Dihydropyridine (DHP) is an important organic compound with biological activity and is widely used in drug research. However, there are few studies on its optical properties, especially in the design of viscous fluorescent probes. In this study, a fluorescent probe for viscosity detection using 1,4-dihydropyridine as the fluorophore and indole iodide salt as the recognition group was designed and synthesized. The probe has the advantages of a deep-red emission, low cytotoxicity, good biocompatibility and excellent anti-interference ability. In addition, the probe also has the ability to target mitochondria and has been successfully applied to the detection of the viscosity response of HeLa cells and living mice, and has good clinical application potential.

Designing a Red-Emitting Viscosity-Sensitive BODIPY Fluorophore for Intracellular Viscosity Imaging

Viscosity imaging at a microscopic scale can provide important information about biosystems, including the development of serious illnesses. Microviscosity imaging is achievable with viscosity-sensitive fluorophores, the most popular of which are based on the BODIPY group. However, most of the BODIPY probes fluoresce green light, whereas the red luminescence is desired for the imaging of biological samples. Designing a new viscosity probe with suitable spectroscopic properties is a challenging task because it is difficult to preserve viscosity sensitivity after modifying the molecular structure. Here we describe how we developed a new red-emitting, viscosity-sensitive, BODIPY fluorophore BP-PH-2M-NO₂ that is suitable for reliable intracellular viscosity imaging of lipid droplets in MCF-7 breast cancer cells. The design of BP-PH-2M-NO₂ was aided by DFT calculations that allowed a successful prediction of the viscosity sensitivity of fluorophores before synthesis. In summary, we report a new red viscosity probe possessing monoexponential fluorescence decay that makes it attractive for lifetime-based viscosity imaging.

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 novel water-soluble near-infrared fluorescent probe for monitoring mitochondrial viscosity

Mitochondria, the main source of energy of cells, play a significant role in aerobic respiration process. Some stimulants can result in changes of mitochondrial microenvironments such as viscosity, pH and polarity. Abnormal changes of mitochondrial viscosity have been shown to relate to pathological activities and diseases. Therefore, it is critical to focus our attention on mitochondrial viscosity under different conditions. A novel organic water-soluble molecule called JLQL that could monitor viscosity was conveniently synthesized in two steps. The near-infrared sensor with maximum emission wavelength of 734.6 nm and the Stokes shift of 134.6 nm consisted of a fluorophore and a mitochondrial-targeting moiety as an acceptor group; the two were connected by a double bond. The fluorescence intensity of the sensor increased 175 times with the enhancement of viscosity of a PBS-glycerol system. The interference of other microenvironments such as pH and polarity and other interference analytes could be reduced. JLQL could sensitively and selectively differentiate different levels of mitochondrial viscosity induced by monensin or nystatin. Furthermore, the probe may provide an attractive way to monitor real-time changes of viscosity during mitophagy. Possessing the above properties, JLQL can potentially be employed as a powerful tool for the observation of mitochondrial viscosity.

Amphiphilic copolymer fluorescent probe for mitochondrial viscosity detection and its application in living cells

The mitochondrial viscosity measurement with the amphiphilic copolymer fluorescent probe (PP) has been successfully revealed for the first time. PP was synthesized, starting from a hydrophobic rhodamine derivative fluorophore and hydrophilic 2-hydroxyethyl acrylate (HEA) by radical polymerization, which could be used to detect mitochondrial viscosity specifically. The systematic investigation demonstrated that the fluorescence emission of PP with a deep red emission increased about 9-fold when the medium is changed from methanol to 99% glycerol, indicating high viscosity dependence. Moreover, PP could self-assemble into nanospheres with the particle size of about 140 nm in water and the nano-structure enabled PP to enter living cells quickly. Cytotoxicity test showed that the cells survival rate remained above 70% at 70 μg·mL^-1 of PP. Good biocompatibility and low cytotoxicity of PP are promising to provide a high contrast fluorescence imaging. Taken together, the results point the way to development of novel amphiphilic copolymer fluorescent probes-based the detection in solutions, physiology and pathology.

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.

Acridinium benzoates for ratiometric fluorescence imaging of cellular viscosity

A series of fluorescent molecular rotors, acridinium benzoates (Acr-A,B,C,D), were designed for ratiometrically monitoring cellular viscosity. High sensitivity to viscosity was observed in probe Acr-A with an insignificant steric effect in the acridinium nitrogen. Acr-A was employed to distinguish cancer cells from normal cells and track the dynamics of viscosity during cellular apoptosis.

A fluorescent molecular rotor probe for tracking plasma membranes and exosomes in living cells

A rotor-based probe MRMP-1 was designed and synthesized. MRMP-1 can bind to plasma membranes very quickly and stably with remarkable fluorescence enhancement. It can be used to monitor the dynamic changes in cell membranes in real-time under stimuli conditions. Importantly, MRMP-1 is the first rotor-based fluorescent sensor to label exosomes in living cells.

A near-infrared fluorescent probe with large Stokes shift for visualizing and monitoring mitochondrial viscosity in live cells and inflammatory tissues

Mitochondria are cellular energy factory, having an essential role in cellular metabolism. Furthermore, abnormal changes in mitochondrial viscosity have been confirmed to be closely related to many diseases. Therefore, the development of probe that responsive to mitochondrial viscosity and its application in mitochondrial viscosity measurement is considered to be a new tool for understanding diseases. In this paper, a mitochondrial viscosity probe (DICB) with a large Stokes shift (214-253 nm) was designed and synthesized by modifying the structure of the carbazole fluorophore. The probe DICB has a favorable responsive to viscosity in the near-infrared (NIR) region (703 nm). In the water-glycerol system (0.893 cP -945 cP), the fluorescence intensity of DICB at 703 nm has a 74 times increase; in the range of 5.041 cP-856.0 cp, it has a well linear fitting relationship. Meantime, the probe has excellent sensitivity to viscosity. The probe (DICB) has been confirmed to be able to detect changes of mitochondrial viscosity in cell models induced by nystatin, carbonyl cyanide m-chlorophenyl hydrazone (CCCP) and lipopolysaccharide (LPS); it has also been validated that DICB can be used in the process of autophagy to monitor mitochondrial viscosity. More importantly, DICB can be applied to the detection of abnormal mitochondrial viscosity in inflammatory tissues at the biological level. The outstanding characteristics of DICB for mitochondrial viscosity detection are not only of great importance to the development of viscosity probes, but also provides a universal strategy to study the relationship between inflammatory and mitochondrial viscosity.

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.

The Effect of Pedal Peptide-Type Neuropeptide on Locomotor Behavior and Muscle Physiology in the Sea Cucumber Apostichopus japonicus

Neuropeptides are endogenous active substances that are present in nervous tissues and participate in behavioral and physiological processes of the animal system. Locomotor behavior is basic to predation, escape, reproduction in animals, and neuropeptides play an important role in locomotion. In this study, the function of pedal peptide-type neuropeptide (PDP) in the process of locomotor behavior of the sea cucumber Apostichopus japonicus was evaluated. The locomotor behavior of A. japonicus was recorded by infrared camera before and after PDP administration, and muscle physiology was studied by ultra performance liquid chromatography and quadrupole time-off-light mass spectrometry (UPLC-Q-TOF-MS) to clarify the potential physiological mechanisms. The results showed that PDP enhanced the cumulative duration of moving significantly at the 7th h after injection, and reduced the mean and maximum velocity by 16.90 and 14.22% in A. japonicus. The data of muscle metabolomics suggested that some significantly changed metabolites were related to locomotor behavior of sea cucumbers. The decreases of phosphatidylethanolamine (PE) and phosphatidylcholine (PC) might result in the increases of lysophosphatidylcholines (lysoPC) and lysophosphatidylethanolamine (lysoPE), and suggested the change of fluidity and permeability in the muscle cell membrane, which would affect the physiology and function of muscle cells, and finally alter the locomotor behavior. In addition, the increased level of arachidonic acid (ARA) might activate K⁺ ion channels and then affect the signaling of muscle cells, or promote the sensitivity of muscle cells to Ca²⁺ and then result in the contractility of longitudinal muscles in sea cucumbers. ARA was also involved in the linoleic acid metabolism which was the only pathway that disturbed significantly after PDP administration. In conclusion, PDP participated in the regulation of locomotor behavior in the sea cucumber, and the decreased PE and PC, increased lysoPC, lysoPE and ARA might be the potential physiological mechanisms that responsible for behavioral effects of PDP in A. japonicus.

Metabolome profiling in skeletal muscle to characterize metabolic alterations in over-conditioned cows during the periparturient period

The transition from late gestation to early lactation is associated with extensive changes in metabolic, endocrine, and immune functions in dairy cows. Skeletal muscle plays an important role in maintaining the homeorhetic adaptation to the metabolic needs of lactation. The objective of this study was to characterize the skeletal muscle metabolome in the context of the metabolic changes that occur during the transition period in dairy cows with high (HBCS) versus normal body condition (NBCS). Fifteen weeks antepartum, 38 pregnant multiparous Holstein cows were assigned to 1 of 2 groups, which were fed differently to reach the targeted BCS and back fat thickness (BFT) until dry-off at -49 d before calving (HBCS: >3.75 and >1.4 cm; NBCS: <3.5 and <1.2 cm). During the dry period and the subsequent lactation, both groups were fed identical diets. The differences in both BCS and BFT were maintained throughout the study. The metabolome was characterized in skeletal muscle samples (semitendinosus muscle) collected on d -49, 3, 21, and 84 relative to calving using a targeted metabolomics approach (AbsoluteIDQ p180 kit; Biocrates Life Sciences AG, Innsbruck, Austria), which allowed for the quantification of up to 188 metabolites from 6 different compound classes (acylcarnitines, amino acids, biogenic amines, glycerophospholipids, sphingolipids, and hexoses). On d -49, the concentrations of citrulline and hydroxytetradecadienyl-l-carnitine in muscle were higher in HBCS cows than in NBCS cows, but those of carnosine were lower. Over-conditioning did not affect the muscle concentrations of any of the metabolites on d 3. On d 21, the concentrations of phenylethylamine and linoleylcarnitine in muscle were lower in HBCS cows than in NBCS cows, and the opposite was true for lysophosphatidylcholine acyl C20:4. On d 84, the significantly changed metabolites were mainly long-chain (>C32) acyl-alkyl phosphatidylcholine and di-acyl phosphatidylcholine, along with 3 long-chain (>C16) sphingomyelin that were all lower in HBCS cows than in NBCS cows. These data contribute to a better understanding of the metabolic adaptation in skeletal muscle of dairy cows during the transition period, although the physiological significance and underlying molecular mechanisms responsible for the regulation of citrulline, hydroxytetradecadienyl-l-carnitine, carnosine, and phenylethylamine associated with over-conditioning are still elusive and warrant further investigation. The changes observed in muscle lysophosphatidylcholine and phosphatidylcholine concentrations may point to an alteration in phosphatidylcholine metabolism, probably resulting in an increase in membrane stiffness, which may lead to abnormalities in insulin signaling in the muscle of over-conditioned cows.

The effect of solvent polarity and macromolecular crowding on the viscosity sensitivity of a molecular rotor BODIPY-C10

Viscosity is the key parameter of many biological systems such as live cells. It can be conveniently measured with ‘molecular rotors’ – fluorescent sensors of microviscosity. Here, we investigate one of the most applied molecular rotors BODIPY-C₁₀.

Functionalized BODIPYs as Fluorescent Molecular Rotors for Viscosity Detection

Abnormal changes of intracellular microviscosity are associated with a series of pathologies and diseases. Therefore, monitoring viscosity at cellular and subcellular levels is important for pathological research. Fluorescent molecular rotors (FMRs) have recently been developed to detect viscosity through a linear correlation between fluorescence intensity or lifetime and viscosity. Recently, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (boron dipyrrins or BODIPY) derivatives have been widely used to build FMRs for viscosity probes due to their high rotational ability of the rotor and potentially high brightness. In this minireview, functionalized BODIPYs as FMRs for viscosity detection were collected, analyzed and summarized.

Rational Design of a Rigid Fluorophore-Molecular Rotor-Based Probe for High Signal-to-Background Ratio Detection of Sulfur Dioxide in Viscous System

Many viscous microenvironments exist in living systems. For instance, at the cellular level, the viscosity of subcellular organelles (mitochondria, lysosomes, endoplasmic reticulum, nucleus, etc.) is much greater than that of cytoplasm; at the organismal level, compared with normal states of health, blood, or lymphatic fluid viscosity will increase to some extent in diabetes, hypertension, inflammation, tumors, and so on. However, due to the design shortcoming, there is a lack of efficient tools for detecting biomolecules in viscous living systems. Herein, we propose a rational design strategy for constructing ratiometric fluorescent probes with superior response signal-to-background (S/B) ratio in viscous systems based on rigid-fluorophore-molecular rotor platform, and a practical sulfur dioxide (SO₂) probe (RFC-MRC) based on conmarin-cyanine dyad was prepared as a proof-of-concept. The probe performs a significant enhancement (71.5-fold) of ratiometric response signal stimulated by SO₂ in viscous aqueous media. The cationic probe can selectively in mitochondria and was successfully utilized to sense SO₂ in living HeLa cells through ratiometric fluorescence imaging. What's more, in the fluorescence imaging experiments of monitoring SO₂ in apoptotic cells using probe RFC-MRC, a more obvious superior of S/B ratio was observed in the early apoptotic cells than in the lately apoptotic cells.

Ferroptosis Accompanied by •OH Generation and Cytoplasmic Viscosity Increase Revealed via Dual-Functional Fluorescence Probe

Ferroptosis, a new form of regulated cell death, results from the iron-dependent accumulation of lipid peroxides that are associated with reactive oxygen species. However, it remains unclear how hydroxyl radical (^•OH) and cellular microenvironments such as viscosity alter in this process. Herein, we characterize for the first time the changing behavior of ^•OH and cytoplasmic viscosity during ferroptosis using a dual-functional fluorescence probe (H-V) that is designed via the molecular rotor strategy and the unique aromatic hydroxylation of ^•OH. Probe H-V shows completely separate spectral responses to ^•OH and viscosity with high sensitivity and selectivity, thereby achieving the detection of ^•OH and viscosity in two independent channels without spectral cross-interference. With the probe we find that ferroptosis is accompanied by significant ^•OH generation and cytoplasmic viscosity increase. Most notably, the raised ^•OH comprises the majority of the total reactive oxygen species in ferroptosis. H-V is biocompatible, ready to prepare, and may be expected to be used in the study of viscosity and ^•OH detection in more biosystems.

Sensing and imaging of mitochondrial viscosity in living cells using a red fluorescent probe with a long lifetime

A red fluorescent probe (Mito-V) with a long lifetime was designed to monitor viscosity changes with high selectivity and sensitivity. The fluorescence intensity and lifetime of Mito-V displayed a good relationship with the viscosity value, and Mito-V was successfully applied to sensing mitochondrial viscosity changes in living cells under different biological processes.

Immobilizable fluorescent probes for monitoring the mitochondria microenvironment: a next step from the classic

Immobilizable probes represent a valuable trend.

A red-emissive mitochondrial probe for imaging of the viscosity in living cells

L can exclusively stain mitochondria and monitor the mitochondrial viscosity changes.

Dual-functional fluorescent molecular rotor for endoplasmic reticulum microviscosity imaging during reticulophagy

A dual functional fluorescent molecular rotor was developed to trigger intracellular ER autophagy and quantify the local viscosity variations by FLIM imaging.

Monitoring mitochondrial viscosity with anticancer phosphorescent Ir(iii) complexes via two-photon lifetime imaging

Precise quantitative measurement of viscosity at the subcellular level presents great challenges. Two-photon phosphorescence lifetime imaging microscopy (TPPLIM) can reflect micro-environmental changes of a chromophore in a quantitative manner. Phosphorescent iridium complexes are potential TPPLIM probes due to their rich photophysical properties including environment-sensitive long-lifetime emission and high two-photon absorption (TPA) properties. In this work, a series of iridium(iii) complexes containing rotatable groups are developed as mitochondria-targeting anticancer agents and quantitative viscosity probes. Among them, Ir6 ([Ir(ppy-CHO)₂(dppe)]PF₆; ppy-CHO: 4-(2-pyridyl)benzaldehyde; dppe: cis-1,2-bis(diphenylphosphino)ethene) shows satisfactory TPA properties and long lifetimes (up to 1 μs). The emission intensities and lifetimes of Ir6 are viscosity-dependent, which is mainly attributed to the configurational changes in the diphosphine ligand as proved by ¹H NMR spectra. Ir6 displays potent cytotoxicity, and mechanism investigations show that it can accumulate in mitochondria and induce apoptotic cell death. Moreover, Ir6 can induce mitochondrial dysfunction and monitor the changes in mitochondrial viscosity simultaneously in a real-time and quantitative manner via TPPLIM. Upon Ir6 treatment, a time-dependent increase in viscosity and heterogeneity is observed along with the loss of membrane potential in mitochondria. In summary, our work shows that multifunctional phosphorescent metal complexes can induce and precisely detect microenvironmental changes simultaneously at the subcellular level using TPPLIM, which may deepen the understanding of the cell death mechanisms induced by these metallocompounds.

The effect of cinnamon on polycystic ovary syndrome in a mouse model

BACKGROUND

Polycystic ovary syndrome (PCOS) is the most prevalent cause of anovulatory infertility and hyperandrogenism. Evidence favors insulin resistance and compensatory hyperinsulinemia as the predominant, perhaps primary, defects in PCOS. The use of insulin-sensitizing drugs has been shown to improve both the reproductive and the metabolic aspects of PCOS. Cinnamon has been found to have insulin sensitizing effect and improve menstrual cyclicity in women with PCOS. The aim of this study was to determine the effect and mechanism of cinnamon on PCOS using a dehydroepiandrosterone (DHEA) induced PCOS mouse model.

METHODS

Prepubertal C57BL/6 mice (age 25 days) were raised to developed into control group, DHEA group and DHEA plus cinnamon group for 20 days. The stages of the estrous cycle were determined based on vaginal cytology; metabolic characteristics were examined by intraperitoneal glucose tolerance test and insulin tolerance test, the serum levels of hormones (testosterone, insulin, LH, FSH, IGF-1, IGFBP-1) were checked using enzyme-linked immunosorbent assay (ELISA) method, the ovarian morphology was observed by stained with hematoxylin and eosin. IGF-1 and IGFBP-1 expression in ovary were detected by immunohistochemical stain.

RESULTS

Cinnamon restores the cyclicity and ovary morphology in PCOS mice model induced by DHEA. There are significant differences of serum level of total testosterone (0.033 ± 0.009 ng/ml), among control group, DHEA and cinnamon group (0.052 ± 0.011 ng/ml), and DHEA group (0.079 ± 0.015 ng/ml); There was an increasing tendency of serum FSH level from DHEA group (5.02 ± 0.31 ng/ml), DHEA and cinnamon group (5.81 ± 0.51 ng/ml), to control group (7.13 ± 0.74 ng/ml); and there was a decreasing trend of serum LH level from DHEA group (3.75 ± 0.57 ng/ml), DHEA and cinnamon group (1.35 ± 0.61 ng/ml), or control group (0.69 ± 0.34 ng/ml); serum insulin level is significantly higher in DHEA treated mice (1.61 ± 0.31 ng/ml) than control group (0.93 ± 0.19 ng/ml), or DHEA and cinnamon effect (1.27 ± 0.23 ng/ml) (p < 0.05). The DHEA group also has a higher serum IGF-1 level (0.35 ± 0.06 ng/ml) than control group (0.17 ± 0.04 ng/ml) or DHEA and cinnamon group (0.21 ± 0.05 ng/ml) (p < 0.05). While DHEA group has a lower IGFBP-1 level (5.5 ± 1.6 ng/ml) than control group (15.8 ± 2.1 ng/ml) or DHEA and cinnamon group (10.3 ± 2.5 ng/ml) (p < 0.05). Cinnamon also attenuates DHEA induced a higher IGF-1 and lower IGFBP-1 expression in ovary by immunohistochemistry.

CONCLUSIONS

These preliminary data suggest that cinnamon supplementation improves insulin resistance and may be a potential therapeutic agent for the treatment of PCOS.

Skeletal muscle phosphatidylcholine and phosphatidylethanolamine respond to exercise and influence insulin sensitivity in men

Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) composition in skeletal muscle have been linked to insulin sensitivity. We evaluated the relationships between skeletal muscle PC:PE, physical exercise and insulin sensitivity. We performed lipidomics and measured PC and PE in m. vastus lateralis biopsies obtained from 13 normoglycemic normal weight men and 13 dysglycemic overweight men at rest, immediately after 45 min of cycling at 70% maximum oxygen uptake, and 2 h post-exercise, before as well as after 12 weeks of combined endurance- and strength-exercise intervention. Insulin sensitivity was monitored by euglycemic-hyperinsulinemic clamp. RNA-sequencing was performed on biopsies, and mitochondria and lipid droplets were quantified on electron microscopic images. Exercise intervention for 12 w enhanced insulin sensitivity by 33%, skeletal muscle levels of PC by 21%, PE by 42%, and reduced PC:PE by 16%. One bicycle session reduced PC:PE by 5%. PC:PE correlated negatively with insulin sensitivity (β = -1.6, P < 0.001), percent area of mitochondria (ρ = -0.52, P = 0.035), and lipid droplet area (ρ = 0.55, P = 0.017) on EM pictures, and negatively with oxidative phosphorylation and mTOR based on RNA-sequencing. In conclusion, PC and PE contents of skeletal muscle respond to exercise, and PC:PE is inversely related to insulin sensitivity.

A nontoxic, photostable and high signal-to-noise ratio mitochondrial probe with mitochondrial membrane potential and viscosity detectivity

Herein, we reported a yellow emission probe 1-methyl-4-(6-morpholino-1, 3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl) pyridin-1-ium iodide which could specifically stain mitochondria in living immortalized and normal cells. In comparison to the common mitochondria tracker (Mitotracker Deep Red, MTDR), this probe was nontoxic, photostable and ultrahigh signal-to-noise ratio, which could real-time monitor mitochondria for a long time. Moreover, this probe also showed high sensitivity towards mitochondrial membrane potential and intramitochondrial viscosity change. Consequently, this probe was used for imaging mitochondria, detecting changes in mitochondrial membrane potential and intramitochondrial viscosity in physiological and pathological processes.

A luminescent bimetallic iridium(iii) complex for ratiometric tracking intracellular viscosity

The luminescent bimetallic iridium probe C10 could distinguish cancer cells from normal cells and track viscosity changes during cell apoptosis.

Membrane lipid alterations in the metabolic syndrome and the role of dietary oils

The metabolic syndrome is a cluster of pathological conditions, including hypertension, hyperglycemia, hypertriglyceridemia, obesity and low HDL levels that is of great concern worldwide, as individuals with metabolic syndrome have an increased risk of type-2 diabetes and cardiovascular disease. Insulin resistance, the key feature of the metabolic syndrome, might be at the same time cause and consequence of impaired lipid composition in plasma membranes of insulin-sensitive tissues like liver, muscle and adipose tissue. Diet intervention has been proposed as a powerful tool to prevent the development of the metabolic syndrome, since healthy diets have been shown to have a protective role against the components of the metabolic syndrome. Particularly, dietary fatty acids are capable of modulating the deleterious effects of these conditions, among other mechanisms, by modifications of the lipid composition of the membranes in insulin-sensitive tissues. However, there is still scarce data based of high-level evidence on the effects of dietary oils on the effects of the metabolic syndrome and its components. This review summarizes the current knowledge on the effects of dietary oils on improving alterations of the components of the metabolic syndrome. It also examines their influence in the modulation of plasma membrane lipid composition and in the functionality of membrane proteins involved in insulin activity, like the insulin receptor, GLUT-4, CD36/FAT and ABCA-1, and their effect in the metabolism of glucose, fatty acids and cholesterol, and, in turn, the key features of the metabolic syndrome. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.

Relaxation-based viscosity mapping for magnetic particle imaging

Magnetic particle imaging (MPI) has been shown to provide remarkable contrast for imaging applications such as angiography, stem cell tracking, and cancer imaging. Recently, there is growing interest in the functional imaging capabilities of MPI, where 'color MPI' techniques have explored separating different nanoparticles, which could potentially be used to distinguish nanoparticles in different states or environments. Viscosity mapping is a promising functional imaging application for MPI, as increased viscosity levels in vivo have been associated with numerous diseases such as hypertension, atherosclerosis, and cancer. In this work, we propose a viscosity mapping technique for MPI through the estimation of the relaxation time constant of the nanoparticles. Importantly, the proposed time constant estimation scheme does not require any prior information regarding the nanoparticles. We validate this method with extensive experiments in an in-house magnetic particle spectroscopy (MPS) setup at four different frequencies (between 250 Hz and 10.8 kHz) and at three different field strengths (between 5 mT and 15 mT) for viscosities ranging between 0.89 mPa · s-15.33 mPa · s. Our results demonstrate the viscosity mapping ability of MPI in the biologically relevant viscosity range.

Imaging tumor microscopic viscosity in vivo using molecular rotors

The microscopic viscosity plays an essential role in cellular biophysics by controlling the rates of diffusion and bimolecular reactions within the cell interior. While several approaches have emerged that have allowed the measurement of viscosity and diffusion on a single cell level in vitro, the in vivo viscosity monitoring has not yet been realized. Here we report the use of fluorescent molecular rotors in combination with Fluorescence Lifetime Imaging Microscopy (FLIM) to image microscopic viscosity in vivo, both on a single cell level and in connecting tissues of subcutaneous tumors in mice. We find that viscosities recorded from single tumor cells in vivo correlate well with the in vitro values from the same cancer cell line. Importantly, our new method allows both imaging and dynamic monitoring of viscosity changes in real time in live animals and thus it is particularly suitable for diagnostics and monitoring of the progress of treatments that might be accompanied by changes in microscopic viscosity.