A specific dual-locked fluorescence probe to visualize the dynamic changes of lipid droplets and hypochlorous acid in inflammation

Inflammation is a key factor leading to the occurrence and development of many diseases, both lipid droplets (LDs) and hypochlorous acid (HClO/ClO-) are regarded as the important biomarkers of inflammation. Therefore, it is of great significance to develop an efficient single chemical sensor that can simultaneously detect these two biomarkers. To achieve the goal, we developed a dual-locked fluorescence probe (TPA-DNP) by fusing two targets activated reporting system, its implementation was achieved by turning-on the fluorescence of TPA-DNP through LDs and HClO/ClO- simultaneously. In simulated LDs environment, TPA-DNP displayed excellent selectivity to HClO/ClO-, high sensitivity (LOD = 0.527 μM) and strong anti-interference ability. In addition, cell and zebrafish imaging experiments showed that TPA-DNP could be utilized to visualize exogenous/endogenous HClO/ClO- in LDs environment, and could also be used to observe the impact of LDs changes on the HClO/ClO- detection. On the basis, TPA-DNP served as a favorable tool to achieve visualization of inflammatory dynamic changes.

Liquid core fluorescent organic nanoprobes: Long-term stability and highly selective lipid droplets bio-imaging

Lipid droplets (LDs) are important subcellular organelles that play a huge role in cell metabolism and growth. In this study, we synthesized two LDs fluorescent probes with benzothiadiazole (BTH) as electron acceptor and triphenylamine (TPA) as electron donor, which named as TPA-BTH1 and TPA-BTH2, respectively. Meanwhile, we introduced long alkyl chain to the probe as a shielding group and LDs targeting enhancement group. The results showed that the two probes were too sensitive to solvents' polarity because of the D-A structures possessed twisted intramolecular charge-transfer (TICT) effect. Furthermore, we prepared the two probes into nanoprobes by nanoprecipitation, which named as TPA-BTH1-20 and TPA-BTH2-20, respectively. The nanoprobes also had excellent fluorescence emission abilities and biocompatibility, as well as high photostability and accurately target LDs ability, which could be successfully applied in cell fluorescence imaging experiments.

FOXO3 Deficiency in Neutrophils Drives Colonic Inflammation and Tumorigenesis

Inflammatory bowel disease (IBD), characterized by infiltration of polymorphonuclear neutrophils (PMNs), increases the risk of colon cancer. PMN activation corresponds to the accumulation of intracellular Lipid Droplets (LDs). As increased LDs are negatively regulated by transcription factor Forkhead Box O3 (FOXO3), we aim to determine the significance of this regulatory network in PMN-mediated IBD and tumorigenesis. Affected tissue of IBD and colon cancer patients, colonic and infiltrated immune cells, have increased LDs' coat protein, PLIN2. Mouse peritoneal PMNs with stimulated LDs and FOXO3 deficiency have elevated transmigratory activity. Transcriptomic analysis of these FOXO3-deficient PMNs showed differentially expressed genes (DEGs; FDR < 0.05) involved in metabolism, inflammation, and tumorigenesis. Upstream regulators of these DEGs, similar to colonic inflammation and dysplasia in mice, were linked to IBD and human colon cancer. Additionally, a transcriptional signature representing FOXO3-deficient PMNs (PMN-FOXO3₃₈₉) separated transcriptomes of affected tissue in IBD (p = 0.00018) and colon cancer (p = 0.0037) from control. Increased PMN-FOXO3₃₈₉ presence predicted colon cancer invasion (lymphovascular p = 0.015; vascular p = 0.046; perineural p = 0.03) and poor survival. Validated DEGs from PMN-FOXO3₃₈₉ (P2RX1, MGLL, MCAM, CDKN1A, RALBP1, CCPG1, PLA2G7) are involved in metabolism, inflammation, and tumorigenesis (p < 0.05). These findings highlight the significance of LDs and FOXO3-mediated PMN functions that promote colonic pathobiology.

The Janus-Faced Role of Lipid Droplets in Aging: Insights from the Cellular Perspective

It is widely accepted that nine hallmarks-including mitochondrial dysfunction, epigenetic alterations, and loss of proteostasis-exist that describe the cellular aging process. Adding to this, a well-described cell organelle in the metabolic context, namely, lipid droplets, also accumulates with increasing age, which can be regarded as a further aging-associated process. Independently of their essential role as fat stores, lipid droplets are also able to control cell integrity by mitigating lipotoxic and proteotoxic insults. As we will show in this review, numerous longevity interventions (such as mTOR inhibition) also lead to strong accumulation of lipid droplets in Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster, and mammalian cells, just to name a few examples. In mammals, due to the variety of different cell types and tissues, the role of lipid droplets during the aging process is much more complex. Using selected diseases associated with aging, such as Alzheimer's disease, Parkinson's disease, type II diabetes, and cardiovascular disease, we show that lipid droplets are "Janus"-faced. In an early phase of the disease, lipid droplets mitigate the toxicity of lipid peroxidation and protein aggregates, but in a later phase of the disease, a strong accumulation of lipid droplets can cause problems for cells and tissues.

AmAtg2B-Mediated Lipophagy Regulates Lipolysis of Pupae in Apis mellifera

Lipophagy plays an important role in regulating lipid metabolism in mammals. The exact function of autophagy-related protein 2 (Atg2) has been investigated in mammals, but research on the existence and functions of Atg2 in Apis mellifera (AmAtg2) is still limited. Here, autophagy occurred in honeybee pupae, which targeted lipid droplets (LDs) in fat body, namely lipophagy, which was verified by co-localization of LDs with microtubule-associated protein 1A/1B light chain 3 beta (LC3). Moreover, AmAtg2 homolog B (AmAtg2B) was expressed specifically in pupal fat body, which indicated that AmAtg2B might have special function in fat body. Further, AmAtg2B antibody neutralization and AmAtg2B knock-down were undertaken to verify the functions in pupae. Results showed that low expression of AmAtg2B at the protein and transcriptional levels led to lipophagy inhibition, which down-regulated the expression levels of proteins and genes related to lipolysis. Altogether, results in this study systematically revealed that AmAtg2B interfered with lipophagy and then caused abnormal lipolysis in the pupal stage.

Optimal Stage for Cryotop Vitrification of Porcine Embryos

Different development stages of porcine embryos have different tolerance to low temperature. Therefore, we took the porcine embryos after parthenogenetic activation (PA) as the model, to explore the optimal development stage for vitrification during morula (D4), early blastocyst (D5), and expanded blastocyst (D6) after PA (D0). Embryos were observed with microscope and analyzed by different staining after cryo-recovery for 24 hours. The quality of embryos was damaged after vitrification, including embryonic nuclei, DNA, cytoskeleton, and organelles. The re-expansion rate at 24 hours of D5 embryos was significantly higher than those of D4 and D6 embryos (D5 vs. D4 vs. D6, 27.620 ± 0.041 vs. 7.809 ± 0.027 vs. 13.970 ± 0.032, p < 0.05). Therefore, D5 embryos were selected as research objects to explore the effect of vitrification on lipid in vitrified embryos. The results showed that the expression levels of perilipin PLIN3 messenger RNA (mRNA) and triacylglycerol synthesis-related genes AGPAT1 and DGAT mRNA are significantly reduced (p < 0.05). Vitrification affected lipid synthesis, which might have an irreversible impact on embryonic development. In conclusion, our data demonstrated that the optimal stage of vitrification was D5 for early blastocysts.

Synthesis of a new environment-sensitive fluorescent probe based on TICT and application for detection of human serum albumin and specific lipid droplets imaging

Environment-sensitive fluorescent probes have always been as forceful tools to understand the pathophysiological processes of relevant diseases. In this work, a new fluorescent probe with typical D-π-A structure was designed and showed high sensitivity to polarity and viscosity changes. DPAR could selectively detect human serum albumin (HSA) with turn-on orange emission in aqueous PBS buffer (pH 7.4), which showed advantages such as rapid response (4 min), high sensitivity (LOD 0.98 μg/mL). Therefore, it was successfully used for achieving HSA levels in urine samples and HSA imaging in HeLa cells. DPAR also exhibited the capability to recognize the cancer cells over the normal cells by lower polarity guided lipid droplets (LDs) imaging (in green emission channel). The detection mechanism for HSA and cancer diagnosis was convinced that DPAR encountered the lower-polarity and higher-viscosity microenvironment, resulting in the confinement of the TICT process and intramolecular rotation. These facts showed that DPAR had good application prospects in environment-related biomedical research and clinical diagnosis.

Kaempferol alleviates LD-mitochondrial damage by promoting autophagy: Implications in Parkinson's disease

Emerging evidence indicates that unexpected lipid droplet (LD) deposition and peroxidation can accelerate organelle stress and plays a crucial role in the pathogenesis of neurodegenerative diseases (NDDs). In our previous study, we confirmed that kaempferol (Ka), a natural flavonoid small molecule, exhibited neuroprotective effects on mice with LPS-induced Parkinson's disease (PD). In addition, previous studies have shown that autophagy plays an important role in the regulation of cellular LD deposition. In the current study, we showed that Ka protected against TH⁺ neuronal loss and behavioral deficits in MPTP/p-induced PD mice, accompanied by reduced lipid oxidative stress in the substantia nigra pars compacta (SNpc). In cultured neuronal cells, Ka exhibited a relatively safe concentration range and significantly suppressed LD accumulation and cellular apoptosis induced by MPP⁺. Further study indicated that the protective effect of Ka was dependent on autophagy, specifically lipophagy. Critically, Ka promoted autophagy to mediate LD degradation in lysosomes, which then alleviated lipid deposition and peroxidation and the resulting mitochondrial damage, consequently reducing neuronal death. Furthermore, AAV-shAtg5-mediated Atg5 knockdown abolished the neuroprotective effects of Ka against lipid oxidation in PD mice. This work demonstrates that Ka prevents dopaminergic neuronal degeneration in PD via the inhibition of lipid peroxidation-mediated mitochondrial damage by promoting lipophagy and provides a potential novel therapeutic strategy for PD and related NDDs.

Cholesterol and Mevalonate: Two Metabolites Involved in Breast Cancer Progression and Drug Resistance through the ERRα Pathway

Breast cancer is the second greatest cause of cancer-related death in women. Resistance to endocrine treatments or chemotherapy is a limiting drawback. In this context, this work aims to evaluate the effects of cholesterol and mevalonate during tumor progression and their contribution in the onset of resistance to clinical treatments in use today. In this study, we demonstrated that cholesterol and mevalonate treatments were able to activate the estrogen-related receptor alpha (ERRα) pathway, increasing the expression levels of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), ERbB2/human epithelial receptor (HER2), tumor protein D52 (TPD52), and NOTCH2 proteins in breast cancer cells. The activation of this pathway is shown to be responsible for intense metabolic switching, higher proliferation rates, sustained motility, the propagation of cancer stem-like cells (CSCs), and lipid droplet formation. All of these events are related to greater tumor propagation, aggressiveness, and drug resistance. Furthermore, the activation and expression of proteins induced by the treatment with cholesterol or mevalonate are consistent with those obtained from the MCF-7/TAMr cell line, which is largely used as a breast cancer model of acquired endocrine therapy resistance. Altogether, our data indicate that cholesterol and mevalonate are two metabolites implicated in breast cancer progression, aggressiveness, and drug resistance, through the activation of the ERRα pathway. Our findings enable us to identify the ERRα receptor as a poor prognostic marker in patients with breast carcinoma, suggesting the correlation between cholesterol/mevalonate and ERRα as a new possible target in breast cancer treatment.

ARF1 activation dissociates ADRP from lipid droplets to promote HCV assembly

Lipid droplets are the place for HCV assembly and ADRP is an abundant lipid droplets-associated protein. However, little is known about the mechanisms how ADRP is involved in HCV life cycle. Here we demonstrate that activation of ARF1 dissociates ADRP from lipid droplets. A constitute active form of ARF1 (ARF1Q71I) promotes HCV assembly. We found that ADRP plays a positive role in HCV replication and a negative role in HCV assembly. Overexpression of ADRP increases the size of lipid droplets, while silencing ADRP reduces the size of lipid droplets. These findings provide new insight into the role of lipid droplets proteins in life cycle of HCV.

Lipid droplet remodeling and interaction with mitochondria in mouse brown adipose tissue during cold treatment

Brown adipose tissue (BAT) maintains animal body temperature by non-shivering thermogenesis, which is through uncoupling protein 1 (UCP1) that uncouples oxidative phosphorylation and utilizes β-oxidation of fatty acids released from triacylglycerol (TAG) in lipid droplets (LDs). Increasing BAT activity and "browning" other tissues such as white adipose tissue (WAT) can enhance the expenditure of excess stored energy, and in turn reduce prevalence of metabolic diseases. Although many studies have characterized the biology of BAT and brown adipocytes, BAT LDs especially their activation induced by cold exposure remain to be explored. We have isolated LDs from mouse interscapular BAT and characterized the full proteome using mass spectrometry. Both morphological and biochemical experiments showed that the LDs could tightly associate with mitochondria. Under cold treatment mouse BAT started expressing LD structure protein PLIN-2/ADRP and increased expression of PLIN1. Both hormone sensitive lipase (HSL) and adipose TAG lipase (ATGL) were increased in LDs. In addition, isolated BAT LDs showed increased levels of the mitochondrial protein UCP1, and prolonged cold exposure could stimulate BAT mitochondrial cristae biogenesis. These changes were in agreement with the data from transcriptional analysis. Our results provide the BAT LD proteome for the first time and show that BAT LDs facilitate heat production by coupling increasing TAG hydrolysis through recruitment of ATGL and HSL to the organelle and expression of another LD resident protein PLIN2/ADRP, as well as by tightly associating with activated mitochondria. These findings will benefit the study of BAT activation and the interaction between LDs and mitochondria.

Lysosome-associated protein 1 (LAMP-1) and lysosome-associated protein 2 (LAMP-2) in a larger family carrier of Fabry disease

This study investigated the potential relationship between the expression levels of lysosome-associated membrane proteins (LAMP) 1 and 2 and responses to enzyme replacement therapy (ERT) in the members of a single family with Fabry disease (FD). LAMP levels were assessed by flow cytometry in leukocytes from 17 FD patients who received an eight-month course of ERT course and 101 healthy individuals. We found that phagocytic cells from the FD patients had higher expression levels of both LAMP-1 and LAMP-2, relative to the levels in phagocytes from the healthy controls (p=0.001). Furthermore, the LAMP-1 and LAMP-2 levels in phagocytes from the FD carriers continuously decreased with ERT administration to reach levels similar to those in healthy controls. We suggest that LAMP-1 and LAMP-2 could be used as additional markers with which to assess ERT effectiveness in FD.

High-throughput identification of off-targets for the mechanistic study of severe adverse drug reactions induced by analgesics

Drugs may induce adverse drug reactions (ADRs) when they unexpectedly bind to proteins other than their therapeutic targets. Identification of these undesired protein binding partners, called off-targets, can facilitate toxicity assessment in the early stages of drug development. In this study, a computational framework was introduced for the exploration of idiosyncratic mechanisms underlying analgesic-induced severe adverse drug reactions (SADRs). The putative analgesic-target interactions were predicted by performing reverse docking of analgesics or their active metabolites against human/mammal protein structures in a high-throughput manner. Subsequently, bioinformatics analyses were undertaken to identify ADR-associated proteins (ADRAPs) and pathways. Using the pathways and ADRAPs that this analysis identified, the mechanisms of SADRs such as cardiac disorders were explored. For instance, 53 putative ADRAPs and 24 pathways were linked with cardiac disorders, of which 10 ADRAPs were confirmed by previous experiments. Moreover, it was inferred that pathways such as base excision repair, glycolysis/glyconeogenesis, ErbB signaling, calcium signaling, and phosphatidyl inositol signaling likely play pivotal roles in drug-induced cardiac disorders. In conclusion, our framework offers an opportunity to globally understand SADRs at the molecular level, which has been difficult to realize through experiments. It also provides some valuable clues for drug repurposing.

High glucose, insulin and free fatty acid concentrations synergistically enhance perilipin 3 expression and lipid accumulation in macrophages

OBJECTIVE

Perilipin (PLIN) 3, an intracellular lipid droplet (LD)-associated protein, is implicated in foam cell formation. Since metabolic derangements found in metabolic syndrome, such as high serum levels of glucose, insulin and free fatty acids (FFAs), are major risk factors promoting atherosclerosis, we investigated whether PLIN3 expression is affected by glucose, insulin and oleic acid (OA) using RAW264.7 cells.

METHODS

Real-time PCR and Western blotting were performed to detect PLIN3 or PLIN2 expression. Oil-red O staining and Lipid Analysis were employed to measure cellular content of triacylglycerides (TAG) and cholesterol.

RESULTS

PLIN3 mRNA was stimulated by high glucose or insulin concentrations individually, but not by OA. A combination of any two factors did not enhance PLIN3 expression any more than that evoked by glucose alone at 24h. Interestingly, however, simultaneous addition of all three factors synergistically enhanced the PLIN3 expression. This synergistic effect was not apparent for PLIN2 mRNA expression. Inhibitors of Src family tyrosine kinase and/or phosphatidylinositol 3-kinase, both of which are activated by insulin and FFA signaling, partially suppressed PLIN3 expression induced by the combination of the three factors. While simultaneous addition of glucose, insulin and OA remarkably increased the cellular content of TAG and cholesterol, knocking-down of PLIN3 predominantly reduced TAG content.

CONCLUSIONS

These results indicate that PLIN3 expression is synergistically stimulated by high glucose, insulin and FFA concentrations, in parallel with TAG accumulation in macrophages. This finding raises new evidence of PLIN3 involvement in conversion of macrophages into foam cells.

New insights on glucosylated lipids: metabolism and functions

Ceramide, cholesterol, and phosphatidic acid are major basic structures for cell membrane lipids. These lipids are modified with glucose to generate glucosylceramide (GlcCer), cholesterylglucoside (ChlGlc), and phosphatidylglucoside (PtdGlc), respectively. Glucosylation dramatically changes the functional properties of lipids. For instance, ceramide acts as a strong tumor suppressor that causes apoptosis and cell cycle arrest, while GlcCer has an opposite effect, downregulating ceramide activities. All glucosylated lipids are enriched in lipid rafts or microdomains and play fundamental roles in a variety of cellular processes. In this review, we discuss the biological functions and metabolism of these three glucosylated lipids.