Mammalian lipid droplets: structural, pathological, immunological and anti-toxicological roles

Multiscale and Multimodal Image Fusion. Coping with Differences in Scanned Area and Spatial Resolution for Raman/Fluorescence Images of Labeled Cells

Multiscale and multimodal image fusion is a challenge derived from the diversity of chemical and spatial information provided by the current hyperspectral image platforms. Efficient image fusion approaches are essential to exploit the complementary chemical information across different zoom scales. Most current image fusion algorithms tend to work by equalizing the spatial characteristics of the platforms to be combined, i.e., downsampling pixel size and cropping noncommon scanned sample areas if required. In this work, a new image unmixing algorithm based on a flexible mathematical framework is proposed to enable working with all available image information while preserving the original spatial properties of every imaging measurement. The algorithm is tested on a challenging image fusion scenario of fluorescence and Raman images collected on labeled HeLa cells. The system is relevant from an analytical point of view, since smart fluorescence labeling allows profiting from the excellent morphological information without causing interferences in the rich chemical information furnished by Raman. From a data handling perspective, it offers a challenging multiscale problem, where the fast fluorescence imaging acquisition allows recording full cell images, and the slower Raman image acquisition is focused on scanning only relevant small regions of the cells analyzed. By applying the image fusion algorithm proposed, an improved morphological and chemical characterization of cell constituents in the full cell area is obtained despite the different spatial scales used in the original imaging measurements.

OSBP Participates in Neural Damage Repair by Regulating Lysosome Transport Under Oxidative Stress

Oxidative stress is a major pathological factor in acute brain injury, such as traumatic brain injury (TBI). As highly branched cells, the transport of lysosomes plays a crucial role in neuronal homeostasis. However, the effects and mechanisms of oxidative damage on axonal lysosome transport remain unknown. In this study, we demonstrated that the downregulation of the membrane lipid orchestrator oxysterol-binding protein (OSBP) induced by oxidative stress alters the subcellular distribution of lysosomes in neurons through regulating lysosomal phosphatidylinositol-4-monophosphate (PI(4)P)/phosphatidylinositol-3-monophosphate (PI(3)P) contents, thus disrupting lysosomal transport. The results of the cell experiments confirmed the occurrence of an autophagic pressure burst, disordered anterograde lysosome transport, and an imbalance in the PI(4)P/PI(3)P ratio in neurons after H2O2 treatment. Mechanistically, oxidative damage reduced neuronal OSBP protein levels, thus contributing to lysosomal PI(4)P storage. Furthermore, a protein‒liposome binding assay revealed that compared with liposomes containing PI(4)P, liposomes containing PI(3)P or cholesterol presented decreased coprecipitation of Arl8. The overexpression of OSBP restored the PI(4)P/PI(3)P content, improved the binding ability of Arl8 to bind to lysosomes, increased lysosome localization in neurites, and promoted axonal injury repair. Finally, overexpression of neuronal OSBP through adeno-associated virus intervention in vivo alleviated dendritic damage and improved the neurological function of mice with TBI. Taken together, these findings suggest that disturbance of OSBP induced by oxidative stress results in abnormal lysosomal distribution and contributes to neuronal malfunction in TBI, and OSBP could be a potential target to promote neuronal repair and regeneration by regulating lysosomal lipid composition and axonal localization.

Exploring transcriptomic databases to identify and experimentally validate tissue-specific consensus reference gene for gene expression normalization in BALB/c mice acutely exposed to 2,3,7,8-Tetrachlorodibenzo-p-dioxin

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a toxic compound affecting organs like the liver, kidney, lung, and reproductive systems in mammals. This study outlines a strategy for choosing appropriate HKGs for tissue-specific gene expression analysis in TCDD toxicity, including four steps: i) identifying candidate HKGs from literature and databases; ii) defining primers from literature or designing new ones; iii) validating primer efficiency and specificity; iv) experimentally assessing candidate HKGs' stability in various tissues of TCDD-exposed mice. Based on this strategy, a total of 40 potential HKGs was selected, further filtered based on their database sources and ranked according to their frequency of use or expression stability. Ultimately, we identified a final set of 15 HKGs (Rps18, Calr, Polr2b, Brms1l, P4hb, Esd, Hdgf, Gapdh, Mlec, Tbp, Rn18s, Sdha, B2m, Actr3 and Actb) with typical efficiencies for further evaluation. Then, the stability of the selected HKGs was determined in the liver, kidney, lung, ovary and testis of TCDD-exposed mouse compared to the control group using the [log (2ΔCt)] and statistically analyzed using Pearson correlation coefficient (r) by BestKeeper algorithm. Our data analysis revealed that Actb, Rps18, and Polr2b were the most stable HKGs for normalizing gene expression in the liver, while Sdha, Actb, and Gapdh were suitable for kidney tissue. In the lung, Tbp, Sdha, and Rps18 showed stability, while Tbp, B2m, and Actb were most stable in ovary. Lastly, Actb, B2m, and Tbp were accurately stable in the testis of TCDD-exposed mice. Our study identifies stable HKGs, improving TCDD toxicity research accuracy and reliability.

Accumulation of Damaging Lipids in the Arf1-Ablated Neurons Promotes Neurodegeneration through Releasing mtDNA and Activating Inflammatory Pathways in Microglia

Lipid metabolism disorders in both neurons and glial cells have been found in neurodegenerative (ND) patients and animal models. However, the pathological connection between lipid droplets and NDs remains poorly understood. The recent work has highlighted the utility of a neuron-specific Arf1-knockout mouse model and corresponding cells for elucidating the nexus between lipid metabolism disorders and amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS). In this study, it is found that Arf1 deficiency first induced surplus fatty acid synthesis through the AKT-mTORC1-SREBP1-FASN axis, which further triggered endoplasmic reticulum (ER)-mitochondrial stress cascade via calcium flux. The organelle stress cascade further caused mitochondrial DNA (mtDNA) to be released into cytoplasm. Concurrently, the FASN-driven fatty acid synthesis in the Arf1-deficient neurons might also induce accumulation of sphingolipids in lysosomes that caused dysfunction of autophagy and lysosomes, which further promoted lysosomal stress and mitochondria-derived extracellular vesicles (MDEVs) release. The released MDEVs carried mtDNA into microglia to activate the inflammatory pathways and neurodegeneration. The studies on neuronal lipid droplets (LDs) and recent studies of microglial LDs suggest a unified pathological function of LDs in NDs: activating the inflammatory pathways in microglia. This finding potentially provides new therapeutic strategies for NDs.

Encapsulation of paclitaxel into date palm lipid droplets for enhanced brain cancer therapy

Paclitaxel, a powerful anticancer drug, is limited by its poor water solubility and systemic toxicity, which hinder its effectiveness against aggressive brain tumors. This study aims to overcome these challenges by exploring novel intranasal delivery methods using lipid droplets (LDs) derived from date palm seeds (DPLDs) and mouse liver (MLLDs). The anticancer efficacy of PTX was evaluated using a comparative intranasal delivery approach. The lipid droplets were fractionated, and their physicochemical and biochemical properties were assessed. Our results showed that both DPLDs and MLLDs were spherical, with average diameters of 257 ± 36 nm and 416 ± 83 nm, respectively, and contained oil-rich cores of 392.5 and 612.4 mg mL-1. The MLLDs displayed a distinct lipid profile with low triglyceride content and high monoglyceride and diglyceride content. Conversely, the DPLDs primarily consisted of triglycerides, with stable granularity at around 83% and 79% for MLLDs and DPLDs, respectively. Both lipid droplets showed high encapsulation efficiencies, reaching 48.6 ± 3.2% and 45.4 ± 2.4% for MLLDs and DPLDs, respectively, after 4 h of incubation. The bio-distribution kinetics of paclitaxel post-intranasal administration demonstrated lower plasma paclitaxel levels in formulations compared to free paclitaxel. Notably, the accumulation of paclitaxel in the brain was significantly higher for paclitaxel-DPLD at early time points, with 1.527 ± 0.1% ID g-1 and 2.4 ± 0.16% ID g-1 at 5 and 30 min, respectively, compared to paclitaxel-MLLD and free paclitaxel. In Conclusion, the study highlights the potential of intranasal DPLD and MLLD formulations for enhanced brain targeting in brain tumor therapy, offering improved paclitaxel delivery and overcoming solubility and toxicity challenges.

Clog P-Guided Development of Multi-Colored Buffering Fluorescent Probes for Super-Resolution Imaging of Lipid Droplet Dynamics

Super-resolution fluorescence imaging of live cells increasingly demands fluorescent probes capable of multi-color and long-term dynamic imaging. Understanding the mechanisms of probe-target recognition is essential for the engineered development of such probes. In this study, it is discovered that the molecular lipid solubility parameter, Clog P, determines the staining performance of fluorescent dyes on lipid droplets (LDs). Fluorescent dyes with Clog P values between 2.5 and 4 can form buffering pools outside LDs, replacing photobleached dyes within LDs to maintain constant fluorescence intensity in LDs, thereby enabling dynamic super-resolution imaging of LDs. Guided by Clog P, four different colored buffering LD probes spanning the visible light spectrum have been developed. Using Structured Illumination Microscopy (SIM), the role of LD dynamics have been tracked during cellular ferroptosis with the secretion, storage, and degradation of overexpressed ACSL3 proteins. It is found that LDs serve as storage sites for these proteins through membrane fusion, and further degrade overexpressed proteins via interactions with organelles like lysosomes or through lipophagy, thereby maintaining cellular homeostasis.

The lipid droplet in cancer: From being a tumor-supporting hallmark to clinical therapy

INTRODUCTION

Abnormal lipid metabolism, one of the hallmarks in cancer, has gradually emerged as a novel target for cancer treatment. As organelles that store and release excess lipids, lipid droplets (LDs) resemble "gears" and facilitate cancer development in the body.

AIM

This review discusses the life cycle of LDs, the relationship between abnormal LDs and cancer hallmarks, and the application of LDs in theragnostic and clinical contexts to provide a contemporary understanding of the role of LDs in cancer.

METHODS

A systematic literature search was conducted in PubMed and SPORTDiscus. Retrieve and summarize clinical trials of drugs that target proteins associated with LD formation using the Clinical Trials website. Create a schematic diagram of lipid droplets in the tumor microenvironment using Adobe Illustrator.

CONCLUSION

As one of the top ten hallmarks of cancer, abnormal lipid metabolism caused by excessive generation of LDs interrelates with other hallmarks. The crosstalk between excessive LDs and intracellular free fatty acids (FFAs) promotes an inflammatory environment that supports tumor growth. Moreover, LDs contribute to cancer metastasis and cell death resistance in vivo. Statins, as HMGCR inhibitors, are promising to be the pioneering commercially available anti-cancer drugs that target LD formation.

Molecular Machinery of Lipid Droplet Degradation and Turnover in Plants

Lipid droplets (LDs) are important organelles conserved across eukaryotes with a fascinating biogenesis and consumption cycle. Recent intensive research has focused on uncovering the cellular biology of LDs, with emphasis on their degradation. Briefly, two major pathways for LD degradation have been recognized: (1) lipolysis, in which lipid degradation is catalyzed by lipases on the LD surface, and (2) lipophagy, in which LDs are degraded by autophagy. Both of these pathways require the collective actions of several lipolytic and proteolytic enzymes, some of which have been purified and analyzed for their in vitro activities. Furthermore, several genes encoding these proteins have been cloned and characterized. In seed plants, seed germination is initiated by the hydrolysis of stored lipids in LDs to provide energy and carbon equivalents for the germinating seedling. However, little is known about the mechanism regulating the LD mobilization. In this review, we focus on recent progress toward understanding how lipids are degraded and the specific pathways that coordinate LD mobilization in plants, aiming to provide an accurate and detailed outline of the process. This will set the stage for future studies of LD dynamics and help to utilize LDs to their full potential.

Female-to-male differential transcription patterns of miRNA-mRNA networks in the livers of dioxin-exposed mice

Non-coding microRNAs (miRNAs) have important roles in regulating the expression of liver mRNAs in response to xenobiotic-exposure, but their roles concerning dioxins such as TCDD (2,3,7,8-Tetrachlorodibenzo-p-dioxin) are less clear. This report concerns the potential implication of liver (class I) and circulating (class II) miRNAs in hepatotoxicity of female and male mice after acute exposure to TCDD. The data show that, of a total of 38 types of miRNAs, the expression of eight miRNAs were upregulated in both female and male mice exposed to TCDD. Inversely, the expression of nine miRNAs were significantly downregulated in both animal genders. Moreover, certain miRNAs were preferentially induced in either females or males. The potential downstream regulatory effects of miRNAs on their target genes was evaluated by determining the expression of three group of genes that are potentially involved in cancer biogenesis, other diseases and in hepatotoxicity. It was found that certain cancer-related genes were more highly expressed females rather than males after exposure to TCDD. Furthermore, a paradoxical female-to-male transcriptional pattern was found for several disease-related and hepatotoxicity-related genes. These results suggest the possibility of developing of new miRNA-specific interfering molecules to address their dysfunctions as caused by TCDD.