Lipid droplets: a cellular organelle vital in cancer cells

Targeting lipid peroxidation-associated ferroptosis suppresses lung carcinoma progression by regulating cell cycle arrest

Lung carcinoma is a frequently encountered cancerous growth that affects the respiratory tract and has a high occurrence rate globally. In light of the ongoing worldwide health emergency, the significance of efficient therapeutic agents and strategies is of utmost importance. A meticulous control of the cell cycle is crucial for comprehending the pathophysiology and molecular causes of lung cancer, as well as for the formulation of efficacious therapeutic medicines. The mechanism by which cells synchronize cell cycle with cell survival and death is still not fully understood. In this study, we demonstrate that the halting of the cell cycle has a strong inhibitory impact on ferroptosis, a specific type of controlled cell death triggered by excessive lipid peroxidation at the membranes of cells. Ferroptosis is halted through the mechanism of cell cycle arrest, which involves the deposition of intracellular lipids mediated by diacylglycerol acyltransferase (DGAT). Excessive amounts of polyunsaturated fatty acids (PUFAs) are stored as triacylglycerols (TAGs) within inactive cells. As a result, inhibiting DGAT causes a rearrangement of PUFAs from TAGs to phospholipids and makes arrested cells more susceptible to ferroptosis. We demonstrate that certain lung cancer cells that are resistant to antimitotic drugs and have a slow-cycling behavior exhibit an increase in lipid droplets. Furthermore, we find that the growth of tumors resistant to 5-fluorouracil, lorlatinib, and docetaxel can be effectively suppressed by a combination treatment involving the use of ferroptosis inducers and DGAT inhibitors, which induces ferroptosis. Collectively, these findings demonstrate the involvement of cell cycle arrest in conferring resistance to ferroptosis and propose a potential therapeutic approach for addressing the challenge of slow-cycling malignancies that exhibit resistance to ferroptosis.

Theory of Lipid Metabolism Disorders in Rhinitis and Asthma (Lipid Droplets)

Lipid droplets are important for the storage of neutral lipids in cells; moreover, they participate in a variety of activities in cells and are multifunctional organelles. In the past few decades, lipid droplets have been extensively studied and found to play important roles in cellular energy balance, signal regulation and metabolic regulation. In particular, the formation and function of lipid droplets in adipocytes and mast cells have received much attention. This article reviews the formation, structure and function of lipid droplets in mast cells and elaborates on the relationship between lipid droplets and both adipocyte metabolism and mast cell-mediated allergic inflammation, to provide ideas for the treatment of allergic inflammation by targeting lipid droplets. This study provides important evidence for the role of lipid metabolism disorders in rhinitis and asthma.

Cytoplasmic Lipid Droplets Predict Worse Prognosis in Diffuse Large B-Cell Lymphoma: Next-Generation Sequencing Deciphering Lipogenic Genes

Burkitt lymphoma is characterized by high cell turnover and numerous cytoplasmic vacuoles that are demonstrated to be lipid droplets (LDs) decorated by adipophilin. By contrast, cytoplasmic vacuoles are variably observed in diffuse large B-cell lymphoma (DLBCL) and less well characterized. In this study, we first validated in DLBCL that cytoplasmic vacuoles are indeed LDs by Oil-red-O stain, Bodipy fluorescent stain, and electron microscopy. Second, in a cohort of DLBCL patients (n=52) we showed that LDs in effusional lymphoma cells were associated with a poorer prognosis (P=0.029, log-rank test) and higher International Prognostic Index (IPI) score (94% vs. 66%, P=0.026) than those without. Moreover, using adipophilin as a surrogate marker for LDs, we found in another cohort of biopsy specimen (n=85) that expression of adipophilin by lymphoma cells predicted a poorer prognosis (P=0.007, log-rank test) and higher IPI score (63% vs. 30%, P=0.005). In addition, whole exome sequencing of effusional DLBCL cells showed LD-positive DLBCL shared genetic features with the MCD (MYD88 and CD79B mutations) subtype and highlighted OSBPL10 and CUBN as the most frequently mutated genes involved in lipogenesis. Whole transcriptome analysis by comparing effusional DLBCL cells with versus without LDs showed upregulation of EHHADH, SLC1A1, CD96, INPP4B, and RNF183 relevant for lymphoma lipogenesis and upregulation of epithelial-mesenchymal transition and KRAS signaling pathways. Higher expression of EHHADH and CD96 were validated in LD-positive clinical samples and LD-rich cell lines than LD-poor cells along with the known lipogenic gene, FASN. Our findings highlight the roles of LDs and adipophilin expression in DLBCL, suggest that these markers may predict prognosis and show that lipogenic genes may be potential therapeutic targets.

Reveal the mechanism of hepatic oxidative stress in mice induced by photo-oxidation milk using multi-omics analysis techniques

INTRODUCTION

Photo-oxidation is recognized as a contributor to the deterioration of milk quality, posing potential safety hazards to human health. However, there has been limited investigation into the impact of consuming photo-oxidized milk on health.

OBJECTIVES

This study employs multi-omics analysis techniques to elucidate the mechanisms by which photo-oxidized milk induces oxidative stress in the liver.

METHODS

Mouse model was used to determine the effect of the gavage administration of milk with varying degrees of photo-oxidation on the mouse liver. The damage degree was established by measuring serum markers indicative of oxidative stress, and with a subsequent histopathological examination of liver tissues. In addition, comprehensive metabolome, lipidome, and transcriptome analyses were conducted to elucidate the underlying molecular mechanisms of hepatic damage caused by photo-oxidized milk.

RESULTS

A significant elevation in the oxidative stress levels and the presence of hepatocellular swelling and inflammation subsequent to the gavage administration of photo-oxidized milk to mice. Significant alterations in the levels of metabolites such as lumichrome, all-trans-retinal, L-valine, phosphatidylglycerol, and phosphatidylcholine within the hepatic tissue of mice. Moreover, photo-oxidized milk exerted a pronounced detrimental impact on the glycerophospholipid metabolism of mice liver. The peroxisome proliferator-activated receptors (PPAR) signaling pathway enrichment appreciated in the animals that consumed photo-oxidized milk further supports the substantial negative influence of photo-oxidized milk on hepatic lipid metabolism. Gene set enrichment and interaction analyses revealed that photo-oxidized milk inhibited the cytochrome P450 pathway in mice, while also affecting other pathways associated with cellular stress response and lipid biosynthesis.

CONCLUSION

This comprehensive study provides significant evidence regarding the potential health risks associated with photo-oxidized milk, particularly in terms of hepatic oxidative damage. It establishes a scientific foundation for assessing the safety of such milk and ensuring the quality of dairy products.

A Naphthalimide Based "Turn-ON" Probe for Wash-Free Imaging of Lipid-Droplet in Living Cells With an Excellent Selectivity

The impacts of dimethylation of 4-Amino-1,8-Naphthalimide (ANI) on its photophysical properties are reported. The resulting 4-DiMe-ANI displays completely different fluorescence properties, conferring it ability to selectively label lipid droplets in living cells. A comprehensive photophysical study revealed that this selectivity arises from an Internal Charge Transfer favored in lipophilic media to the detriment of a non-emissive TICT in more polar media. This results in a very high "LDs/Cytosol" signal ratio, enabling LDs to be imaged with an excellent signal-to-noise ratio, and positioning its performance above that of the BODIPY 493/503 commonly used to image LDs.

Impact of Obesity-Related Endoplasmic Reticulum Stress on Cancer and Associated Molecular Targets

Obesity, characterized by excessive body fat, is closely linked to endoplasmic reticulum (ER) stress, leading to insulin resistance and type 2 diabetes. Inflammatory pathways like c-Jun N-terminal kinase (JNK) worsen insulin resistance, impacting insulin signaling. Moreover, ER stress plays a substantial role in cancer, influencing tumor cell survival and growth by releasing factors like vascular endothelial growth factor (VEGF). The unfolded protein response (UPR) is pivotal in this process, offering both pro-survival and apoptotic pathways. This review offers an extensive exploration of the sophisticated connection between ER stress provoked by obesity and its role in both the onset and advancement of cancer. It delves into the intricate interplay between oncogenic signaling and the pathways associated with ER stress in individuals who are obese. Furthermore, this review sheds light on potential therapeutic strategies aimed at managing ER stress induced by obesity, with a focus on addressing cancer initiation and progression. The potential to alleviate ER stress through therapeutic interventions, which may encompass the use of small molecules, FDA-approved medications, and gene therapy, holds great promise. A more in-depth examination of pathways such as UPR, ER-associated protein degradation (ERAD), autophagy, and epigenetic regulation has the potential to uncover innovative therapeutic approaches and the identification of predictive biomarkers.

Bimodal effects on lipid droplets induced in cancer and non-cancer cells by chemotherapy drugs as revealed with a green-emitting BODIPY fluorescent probe

Lipid droplets (LDs) are cytoplasmic lipid-rich organelles with important roles in lipid storage and metabolism, cell signaling and membrane biosynthesis. Additionally, multiple diseases, such as obesity, fatty liver, cardiovascular diseases and cancer, are related to the metabolic disorders of LDs. In various cancer cells, LD accumulation is associated with resistance to cell death, reduced effectiveness of chemotherapeutic drugs, and increased proliferation and aggressiveness. In this work, we present a new viscosity-sensitive, green-emitting BODIPY probe capable of distinguishing between ordered and disordered lipid phases and selectively internalising into LDs of live cells. Through the use of fluorescence lifetime imaging microscopy (FLIM), we demonstrate that LDs in live cancer (A549) and non-cancer (HEK 293T) cells have vastly different microviscosities. Additionally, we quantify the microviscosity changes in LDs under the influence of DNA-damaging chemotherapy drugs doxorubicin and etoposide. Finally, we show that doxorubicin and etoposide have different effects on the microviscosities of LDs in chemotherapy-resistant A549 cancer cells.

A two-in-one probe: imaging lipid droplets and endoplasmic reticulum in tandem

The endoplasmic reticulum (ER) and lipid droplets (LDs) intricately interact in cellular processes, with the ER serving as a hub for lipid synthesis and LDs acting as storage organelles for lipids. Developing fluorescent probes that can simultaneously visualise the ER and LDs provides a means for real-time and specific visualisation of these subcellular organelles and elucidating their interaction. Herein, we present synthetically simple and novel donor-π-acceptor styryl fluorophores (PFC, PFN and PFB) incorporating pentafluorophenyl (PFP) to demonstrate exquisite discriminative imaging of ER and LD with a single excitation wavelength. The PFP moiety aids the ER selectivity, while the overall hydrophobicity of the molecule aids in the LD targeting. Furthermore, the fluorophores are utilised in studying the changes in size, distribution, and biogenesis of LDs within ER regions after treatment with oleic acid. Strong emission, lower concentrations ∼100 nM requirement, minimal cytotoxicity, and photostability make these fluorophores excellent tools for probing sub-cellular dynamics.

Promoting In Vivo NIR-II Fluorescent Imaging for Lipid in Lipid Metabolism Diseases Diagnosis

Lipid metabolism diseases have become a tremendous risk worldwide, along with the development of productivity and particular attention to public health. It has been an urgent necessity to exploit reliable imaging strategies for lipids and thus to monitor fatty liver diseases. Herein, by converting the NIR-I signal to the NIR-II signal with IR1061 for the monitoring of lipid, the in vivo imaging of fatty liver disease was promoted on the contrast and visual effect. The main advantages of the imaging promotion in this work included a long emission wavelength, rapid response, and high signal-background-ratio (SBR) value. After promoting the NIR-I signal to NIR-II signal, IR1061 achieved higher SBR value and exhibited a dose-dependent fluorescence intensity at 1100 nm along with the increase of the EtOH proportion as well as steady and selective optical responses toward liposomes. IR1061 was further applied in the in vivo imaging of lipid in fatty liver diseases. In spite of the differences in body weight gain and TC level between healthy mice and fatty liver diseases two models, IR1061 achieved high-resolution imaging in the liver region to monitor the fatty liver disease status. This work might be informatic for the clinical diagnosis and therapeutical treatments of fatty liver diseases.

Osteocalcin activates lipophagy via the ADPN-AMPK/PPARα-mTOR signaling pathway in chicken embryonic hepatocyte

Fatty liver hemorrhage syndrome (FLHS) is the leading cause of noninfectious mortality in caged layers worldwide. Osteocalcin (OCN) is a protein secreted by osteoblasts, and its undercarboxylated form (ucOCN) acts as a multifunctional hormone that protects laying hens from FLHS. Lipophagy is a form of selective autophagy that breaks down lipid droplets (LDs) through lysosomes, and defective lipophagy is associated with FLHS. The aim of this study was to investigate the effects of ucOCN on the lipophagy of chicken embryonic hepatocytes and associated the function of the adiponectin (ADPN) signaling pathway. In this study, chicken embryonic hepatocytes were divided into 5 groups: control (CONT), fat emulsion (FE, 10% FE, v/v), FE with ucOCN at 1 ng/mL (FE-LOCN), 3 ng/mL (FE-MOCN), and 9 ng/mL (FE-HOCN). In addition, 4 μM AdipoRon, an adiponectin receptor agonist, was used to investigate the function of ADPN. The results showed that compared with CONT group, FE promoted the levels of phosphorylation of mammalian target of rapamycin (p-mTOR) (P < 0.05) and decreased the mRNA expression of ADNP receptors (AdipoR1 and AdipoR2). Compared with FE group, 3 and 9 ng/mL ucOCN inhibited the levels of autophagy adaptor p62 and p-mTOR (P < 0.05), increased the ratios of LC3-II/LC3-I (P < 0.05) and phosphorylated adenosine 5'-monophosphate-activated protein kinase (p-AMPK)/AMPK (P < 0.05), as well as the levels of peroxisome proliferator-activated receptor α (PPAR-α) and ADPN (P < 0.05). In addition, ucOCN at the tested concentrations increased the colocalization of LC3 and LDs in fatty hepatocytes. Administrated 4 μM AdipoRon activated AdipoR1 and AidpoR2 mRNA expression (P < 0.05), decreased the concentrations of triglyceride (P < 0.05), without effects on cell viability (P > 0.05). AdipoRon also increased the LC3-II/LC3-I ratio (P < 0.05) and the levels of p-AMPK/AMPK and PPAR-α (P < 0.05). In conclusion, the results reveal that ucOCN regulates lipid metabolism by activating lipophagy via the ADPN-AMPK/PPARα-mTOR signaling pathway in chicken embryonic hepatocytes. The results may provide new insights for controlling FLHS in laying hens.

Lipid-Based Nanotechnology: Liposome

Over the past several decades, liposomes have been extensively developed and used for various clinical applications such as in pharmaceutical, cosmetic, and dietetic fields, due to its versatility, biocompatibility, and biodegradability, as well as the ability to enhance the therapeutic index of free drugs. However, some challenges remain unsolved, including liposome premature leakage, manufacturing irreproducibility, and limited translation success. This article reviews various aspects of liposomes, including its advantages, major compositions, and common preparation techniques, and discusses present U.S. FDA-approved, clinical, and preclinical liposomal nanotherapeutics for treating and preventing a variety of human diseases. In addition, we summarize the significance of and challenges in liposome-enabled nanotherapeutic development and hope it provides the fundamental knowledge and concepts about liposomes and their applications and contributions in contemporary pharmaceutical advancement.

Rab18 Drift in Lipid Droplet and Endoplasmic Reticulum Interactions of Adipocytes under Obesogenic Conditions

The adipose tissue stores excess energy in the form of neutral lipids within adipocyte lipid droplets (LDs). The correct function of LDs requires the interaction with other organelles, such as the endoplasmic reticulum (ER) as well as with LD coat-associated proteins, including Rab18, a mediator of intracellular lipid trafficking and ER-LD interaction. Although perturbations of the inter-organelle contact sites have been linked to several diseases, such as cancer, no information regarding ER-LD contact sites in dysfunctional adipocytes from the obese adipose tissue has been published to date. Herein, the ER-LD connection and Rab18 distribution at ER-LD contact sites are examined in adipocytes challenged with fibrosis and inflammatory conditions, which represent known hallmarks of the adipose tissue in obesity. Our results show that adipocytes differentiated in fibrotic conditions caused ER fragmentation, the expansion of ER-LD contact sites, and modified Rab18 dynamics. Likewise, adipocytes exposed to inflammatory conditions favored ER-LD contact, Rab18 accumulation in the ER, and Rab18 redistribution to large LDs. Finally, our studies in human adipocytes supported the suggestion that Rab18 transitions to the LD coat from the ER. Taken together, our results suggest that obesity-related pathogenic processes alter the maintenance of ER-LD interactions and interfere with Rab18 trafficking through these contact sites.

An Overview on Lipid Droplets Accumulation as Novel Target for Acute Myeloid Leukemia Therapy

Metabolic reprogramming is a key alteration in tumorigenesis. In cancer cells, changes in metabolic fluxes are required to cope with large demands on ATP, NADPH, and NADH, as well as carbon skeletons. In particular, dysregulation in lipid metabolism ensures a great energy source for the cells and sustains cell membrane biogenesis and signaling molecules, which are necessary for tumor progression. Increased lipid uptake and synthesis results in intracellular lipid accumulation as lipid droplets (LDs), which in recent years have been considered hallmarks of malignancies. Here, we review current evidence implicating the biogenesis, composition, and functions of lipid droplets in acute myeloid leukemia (AML). This is an aggressive hematological neoplasm originating from the abnormal expansion of myeloid progenitor cells in bone marrow and blood and can be fatal within a few months without treatment. LD accumulation positively correlates with a poor prognosis in AML since it involves the activation of oncogenic signaling pathways and cross-talk between the tumor microenvironment and leukemic cells. Targeting altered LD production could represent a potential therapeutic strategy in AML. From this perspective, we discuss the main inhibitors tested in in vitro AML cell models to block LD formation, which is often associated with leukemia aggressiveness and which may find clinical application in the future.