Toxoplasma gondii Sustains Survival by Regulating Cholesterol Biosynthesis and Uptake via SREBP2 Activation.

Toxoplasma gondii (T. gondii) is an obligate intracellular parasite that cannot biosynthesize cholesterol via the mevalonate pathway, it sources this lipid from its host. We discovered that T. gondii infection upregulated the expression of host cholesterol synthesis related genes HMG-CoA reductase(HMGCR), squalene epoxidase (SQLE) and dehydrocholesterol reductase-7 (DHCR7), and increased the uptake pathway gene low-density lipoprotein receptor (LDLR). We found a protein, sterol regulatory element binding protein 2 (SREBP2), which is the key protein regulating the host cholesterol synthesis and uptake during T. gondii infection. T. gondii induced a dose-dependent nuclear translocation of SREBP2. Knockdown SREBP2 reduced T. gondii-induced cholesterol biosynthesis and uptake. Consequently, the parasite's ability to acquire cholesterol was significantly diminished, impairing its invasion, replication, and bradyzoites development. Interfering cholesterol metabolism using AY9944 effectively inhibited T. gondii replication. In summary, SREBP2 played an important role in T. gondii infection in vitro, serving as a potential target for regulating T. gondii-induced cholesterol metabolism, offering insights into the prevention and treatment of toxoplasmosis.

Glutamine sensing licenses cholesterol synthesis.

The mevalonate pathway produces essential lipid metabolites such as cholesterol. Although this pathway is negatively regulated by metabolic intermediates, little is known of the metabolites that positively regulate its activity. We found that the amino acid glutamine is required to activate the mevalonate pathway. Glutamine starvation inhibited cholesterol synthesis and blocked transcription of the mevalonate pathway-even in the presence of glutamine derivatives such as ammonia and α-ketoglutarate. We pinpointed this glutamine-dependent effect to a loss in the ER-to-Golgi trafficking of SCAP that licenses the activation of SREBP2, the major transcriptional regulator of cholesterol synthesis. Both enforced Golgi-to-ER retro-translocation and the expression of a nuclear SREBP2 rescued mevalonate pathway activity during glutamine starvation. In a cell model of impaired mitochondrial respiration in which glutamine uptake is enhanced, SREBP2 activation and cellular cholesterol were increased. Thus, the mevalonate pathway senses and is activated by glutamine at a previously uncharacterized step, and the modulation of glutamine synthesis may be a strategy to regulate cholesterol levels in pathophysiological conditions.

Quercetin represses cholesterol metabolism and mitigates resistance to cisplatin in oral squamous cell carcinoma by regulating AGR2/AKT/SREBP2 axis.

Purpose: This study aimed to explore the effects of quercetin on cholesterol metabolism and cisplatin sensitivity in oral squamous cell carcinoma (OSCC) cell line (CAL27) and investigate the potential molecular mechanisms. Methods: CAL27 cells were exposed to quercetin or cisplatin after upregulation or downregulation of AGR2. The expression of proteins and genes associated with cholesterol metabolism were assessed. The levels of cholesterol and LDL were also measured, and the cisplatin sensitivity of CAL27 cells was analyzed. Results: RNA high-throughput sequencing revealed that after treatment with quercetin, the expression of AGR2 was significantly reduced in cisplatin-resistant CAL27 cells (CAL-27R), which was associated with lipid metabolism. AGR2 deletion ameliorated but its overexpression exacerbated cisplatin resistance and cholesterol metabolism, evidenced by changes in SQLE, HMGCS, LDLR, and n-SREBP2 expression and cholesterol and LDL levels. Moreover, AGR2 promoted cisplatin resistance by activating the AKT signaling pathway and enhancing SREBP2-mediated cholesterol metabolism. Quercetin increased cisplatin sensitivity by repressing cholesterol metabolism but suppressed the AGR2/AKT/SREBP2 signaling pathway in a concentration-dependent manner. These effects were partly reversed by AGR2 overexpression and AKT activation. Conclusion: Our findings demonstrated that quercetin inhibits cholesterol metabolism and cisplatin resistance in CAL27 cells by modulating the AGR2/AKT/SREBP2 axis.

Let-7f-5p Modulates Lipid Metabolism by Targeting Sterol Regulatory Element-Binding Protein 2 in Response to PRRSV Infection.

Porcine reproductive and respiratory syndrome (PRRS) has caused substantial damage to the pig industry. MicroRNAs (miRNAs) were found to play crucial roles in modulating the pathogenesis of PRRS virus (PRRSV). In the present study, we revealed that PRRSV induced let-7f-5p to influence lipid metabolism to regulate PRRSV pathogenesis. A transcriptome analysis of PRRSV-infected PK15CD163 cells transfected with let-7f-5p mimics or negative control (NC) generated 1718 differentially expressed genes, which were primarily associated with lipid metabolism processes. Furthermore, the master regulator of lipogenesis SREBP2 was found to be directly targeted by let-7f-5p using a dual-luciferase reporter system and Western blotting. The findings demonstrate that let-7f-5p modulates lipogenesis by targeting SREBP2, providing novel insights into miRNA-mediated PRRSV pathogenesis and offering a potential antiviral therapeutic target.

Decreased SREBP2 of the striatal cell relates to disrupted protein degradation in Huntington's disease.

This study delineated the intricate relation between cholesterol metabolism, protein degradation mechanisms, and the pathogenesis of Huntington's disease (HD). Through investigations using both animal models and cellular systems, we have observed significant alterations in cholesterol levels, particularly in the striatum, which is the primary lesion site in HD. Our findings indicate the dysregulation of cholesterol metabolism-related factors, such as LDLR and SREBP2, in HD, which may contribute to disease progression. Additionally, we uncovered disruptions in protein degradation pathways, including decreased neddylated proteins and dysregulated autophagy, which further exacerbated HD pathology. Moreover, our study highlighted the potential therapeutic implications of targeting these pathways. By restoring cholesterol levels and modulating protein degradation mechanisms, particularly through interventions, such as MLN4924, we observed potential improvements in cellular function, as indicated by the increased BDNF levels. These insights underscore the importance of simultaneously addressing cholesterol metabolism and protein degradation to alleviate HD pathology. Collectively, this study provides a basic understanding of the interplay between the decrease of SREBP2 and the dysfunctional protein degradation system derived from disrupted cholesterol metabolism in HD and HD cells.

A high cholesterol diet aggravates experimental colitis through SREBP2-modulated endocytosis and degradation of occludin and Zo-1 proteins.

Disrupted cholesterol homeostasis plays a critical role in the development of multiple diseases, such as cardiovascular disease and cancer. However, the role of cholesterol in inflammatory bowel disease (IBD) remains unclear. In the present study, we investigated whether and how high levels of cholesterol in the diet affect experimental colitis in mice. A normal diet supplemented with 1.25% cholesterol (high cholesterol diet) caused more severe colitis and aggravated the disruption of intestinal tight junction structure, accompanied by higher colonic tissue total cholesterol (TC) levels in a dextran sulfate sodium (DSS)-induced experimental colitis mouse model. Cholesterol aggravated DSS-induced intestinal epithelial barrier impairment and nuclear sterol regulatory element-binding protein 2 (nSREBP2) inhibition both in vivo and in vitro. In addition, nSREBP2 overexpression ameliorated cholesterol-induced intestinal epithelial barrier disruption in Caco2 cells. Interestingly, inhibition of SREBP2 disrupted intestinal epithelial barrier in the absence of cholesterol. Furthermore, SREBP2 regulated the protein expression of tight junction proteins (occludin/Zo-1) via modulating caveolin-1-mediated endocytosis and lysosomal degradation. Analysis of UK Biobank data indicated that, in fully adjusted models, higher serum TC concentrations were an independent protective factor for IBD incidence. The sterol regulatory element-binding factor 2 (SREBF2) gene rs2228313 (G/C) genetic variant was associated with the incidence of IBD and the CC genotype of SREBF2 rs2228313 was associated with higher serum TC levels and decreased the risk of IBD. In summary, a high cholesterol diet aggravates DSS-induced colitis in mice by down-regulating nSREBP2 expression, thereby promoting the endocytic degradation of tight junction proteins. In humans, SREBF2 gene single nucleotide polymorphism rs2228313 and serum TC levels are associated with IBD incidence.

Apigenin Attenuates Transverse Aortic Constriction-Induced Myocardial Hypertrophy: The Key Role of miR-185-5p/SREBP2-Mediated Autophagy.

Introduction: Apigenin is a natural flavonoid compound with promising potential for the attenuation of myocardial hypertrophy (MH). The compound can also modulate the expression of miR-185-5p that both promote MH and suppress autophagy. The current attempts to explain the anti-MH effect of apigenin by focusing on changes in miR-185-5p-mediated autophagy. Methods: Hypertrophic symptoms were induced in rats using transverse aortic constriction (TAC) method and in cardiomyocytes using Ang II and then handled with apigenin. Changes in myocardial function and structure and cell viability and surface area were measured. The role of miR-185-5p in the anti-MH function of apigenin was explored by detecting changes in autophagic processes and miR-185-5p/SREBP2 axis. Results: TAC surgery induced weight increase, structure destruction, and collagen deposition in hearts of model rats. Ang II suppresses cardiomyocyte viability and increased cell surface area. All these impairments were attenuated by apigenin and were associated with the restored level of autophagy. At the molecular level, the expression of miR-185-5p was up-regulated by TAC, while the expression of SREBP2 was down-regulated, which was reserved by apigenin both in vivo and in vitro. The induction of miR-185-5p in cardiomyocytes could counteracted the protective effects of apigenin. Discussion: Collectively, the findings outlined in the current study highlighted that apigenin showed anti-MH effects. The effects were related to the inhibition of miR-185-5p and activation of SREBP, which contributed to the increased autophagy.

LW-213, a derivative of wogonin, triggers reticulophagy-mediated cell death in NSCLC via lysosomal damage combined with NPC1 inhibition.

BACKGROUND: Maintaining intracellular equilibrium is essential for the viability of tumor cells, which tend to be particularly vulnerable to environmental stressors. Consequently, targeting the disruption of this homeostasis offers a promising approach for oncological treatments. LW-213, a novel derivative of wogonin, effectively induces apoptosis in cancer cells by initiating endoplasmic reticulum (ER) stress, although the precise molecular pathways involved remain intricate and multifaceted. PURPOSE: This research aimed to explore how LW-213 prompts apoptosis in non-small cell lung cancer (NSCLC) cells and to clarify the detailed mechanisms that govern this process. METHODS: Various NSCLC cell lines were utilized to delineate the apoptotic effects induced by LW-213. Advanced methodologies, including RNA sequencing (RNA-seq), Western blotting (WB), immunofluorescence (IF), immunoprecipitation (IP), flow cytometry (Fc), real-time quantitative polymerase chain reaction (RT-qPCR), and electron microscopy, were employed to investigate the underlying molecular interactions. The efficacy and mechanistic action of LW-213 were also assessed in a xenograft model using nude mice. RESULTS: We demonstrated that LW-213, a small molecule cationic amphiphilic drug (CAD), inhibited Niemann-Pick C1 (NPC1) function and induced lysosomal membrane damage, thereby activating the phosphoinositide-initiated membrane tethering and lipid transport (PITT) pathway. This activation promoted cholesterol transport from the ER to the lysosome, perpetuating a cholesterol-deficient state in the ER, including massive exocytosis of Ca2+ and activation of FAM134B-mediated reticulophagy. Ultimately, excessive reticulophagy induced lethal ER stress. CONCLUSIONS: In summary, our study elucidates an organelle domino reaction initiated by lysosome damage and a series of self-rescue mechanisms that eventually lead to irreversible lethal effects, revealing a potential drug intervention strategy.

LINC00618 facilitates growth and metastasis of hepatocellular carcinoma via elevating cholesterol synthesis by promoting NSUN2-mediated SREBP2 m5C modification.

Dysregulation of cholesterol metabolism is an important feature of cancer development. There are limited reports on the involvement of lncRNAs in hepatocellular carcinoma (HCC) progression via the cholesterol metabolism pathway. The present study explored the effect of LINC00618 on HCC growth and metastasis, and elucidated the underlying mechanisms involved in cholesterol metabolism. Here, we found that LINC00618 expression was upregulated in cancerous tissues from 30 patients with HCC compared to that in adjacent normal tissues. High expression of LINC00618 was detected in metastatic HCC tissues. LINC00618 is predominantly localized in the nucleus and overexpression of LINC00618 facilitated HCC cell proliferation, migration and EMT progression by promoting cholesterol biosynthesis. Mechanistically, the 1-101nt region of LINC00618 bound to NSUN2. LINC00618 inhibited ubiquitin-proteasome pathway-induced NSUN2 degradation. NSUN2 stabilized by LINC00618 increased m5C modification of SREBP2 and promoted SREBP2 mRNA stability in a YBX1-dependent manner, thereby promoting cholesterol biosynthesis in HCC cells. Moreover, mouse HCC xenograft and lung metastasis models were established by subcutaneous and tail vein injections of MHCC97 cells transfected with or without sh-LINC00618. Silencing LINC00618 impeded HCC growth and metastasis. In conclusion, LINC00618 promoted HCC growth and metastasis by elevating cholesterol synthesis by stabilizing NSUN2 to enhance SREBP2 mRNA stability in an m5C-dependent manner.

Cholesterol dynamics in rabbit liver: High-fat diet, olive oil, and synergistic dietary effects.

BACKGROUND & AIMS: Lipid metabolism disorders contribute to a range of human diseases, including liver-related pathologies. Rabbits, highly sensitive to dietary cholesterol, provide a model for understanding the development of liver disorders. Sterol regulatory element-binding protein isoform 2 (SREBP2) crucially regulates intracellular cholesterol pathways. Extra-virgin olive oil (EVOO) has shown reducing cholesterol levels and restoring liver parameters affected by HFD. The aim was to investigate the molecular impact of an HFD and supplemented with EVOO on rabbit liver cholesterol metabolism. APPROACH & RESULTS: Male rabbits were assigned to dietary cohorts, including control, acute/chronic HFD, sequential HFD with EVOO, and EVOO. Parameters such as serum lipid profiles, hepatic enzymes, body weight, and molecular analyses. After 6 months of HFD, plasma and hepatic cholesterol increased with decreased SREBP2 and 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR) expression. Prolonged HFD increased cholesterol levels, upregulating SREBP2 mRNA and HMGCR protein. Combining this with EVOO lowered cholesterol, increased SREBP2 mRNA, and upregulated low-density lipoprotein receptor (LDLR) expression. HFD-induced metabolic dysfunction-associated fatty liver disease was mitigated by EVOO. In conclusion, the SREBP2 system responds to dietary changes. CONCLUSIONS: In rabbits, the SREBP2 system responds to dietary changes. Acute HFD hinders cholesterol synthesis, while prolonged HFD disrupts regulation, causing SREBP2 upregulation. EVOO intake prompts LDLR upregulation, potentially enhancing cholesterol clearance and restoring hepatic alterations.

HIV-TAT dysregulates microglial lipid metabolism through SREBP2/miR-124 axis: Implication of lipid droplet accumulation microglia in NeuroHIV.

Chronic HIV infection can dysregulate lipid/cholesterol metabolism in the peripheral system, contributing to the higher incidences of diabetes and atherosclerosis in HIV (+) individuals. Recently, accumulating evidence indicate that HIV proteins can also dysregulate lipid/cholesterol metabolism in the brain and such dysregulation could be linked with the pathogenesis of HIV-associated neurological disorders (HAND)/NeuroHIV. To further characterize the association between lipid/cholesterol metabolism and HAND, we employed HIV-inducible transactivator of transcription (iTAT) and control mice to compare their brain lipid profiles. Our results reveal that HIV-iTAT mice possess dysregulated lipid profiles and have increased numbers of lipid droplets (LDs) accumulation microglia (LDAM) in the brains. HIV protein TAT can upregulate LDs formation through enhancing the lipid/cholesterol synthesis in vitro. Mechanistically, HIV-TAT increases the expression of sterol regulatory element-binding protein 2 (SREBP2) through microRNA-124 downregulation. Cholesterol synthesis inhibition can block HIV-TAT-mediated NLRP3 inflammasome activation and microglial activation in vitro as well as mitigate aging-related behavioral impairment and memory deficiency in HIV-iTAT mice. Taken together, our results indicate an inherent role of lipid metabolism and LDAM in the pathogenesis of NeuroHIV (immunometabolism). These findings suggest that LDAM reversal through modulating lipid/cholesterol metabolism could be a novel therapeutic target for ameliorating NeuroHIV symptoms in chronic HIV (+) individuals.

25-Hydroxycholesterol attenuates tumor necrosis factor alpha-induced blood-brain barrier breakdown in vitro.

Intracellular cholesterol metabolism is regulated by the SREBP-2 and LXR signaling pathways. The effects of inflammation on these molecular mechanisms remain poorly studied, especially at the blood-brain barrier (BBB) level. Tumor necrosis factor α (TNFα) is a proinflammatory cytokine associated with BBB dysfunction. Therefore, the aim of our study was to investigate the effects of TNFα on BBB cholesterol metabolism, focusing on its underlying signaling pathways. Using a human in vitro BBB model composed of human brain-like endothelial cells (hBLECs) and brain pericytes (HBPs), we observed that TNFα increases BBB permeability by degrading the tight junction protein CLAUDIN-5 and activating stress signaling pathways in both cell types. TNFα also promotes cholesterol release and decreases cholesterol accumulation and APOE secretion. In hBLECs, the expression of SREBP-2 targets (LDLR and HMGCR) is increased, while ABCA1 expression is decreased. In HBPs, only LDLR and ABCA1 expression is increased. TNFα treatment also induces 25-hydroxycholesterol (25-HC) production, a cholesterol metabolite involved in the immune response and intracellular cholesterol metabolism. 25-HC pretreatment attenuates TNFα-induced BBB leakage and partially alleviates the effects of TNFα on ABCA1, LDLR, and HMGCR expression. Overall, our results suggest that TNFα favors cholesterol efflux via an LXR/ABCA1-independent mechanism at the BBB, while it activates the SREBP-2 pathway. Treatment with 25-HC partially reversed the effect of TNFα on the LXR/SREBP-2 pathways. Our study provides novel perspectives for better understanding cerebrovascular signaling events linked to BBB dysfunction and cholesterol metabolism in neuroinflammatory diseases.

ABCA1 deficiency causes tissue-specific dysregulation of the SREBP2 pathway in mice.

ABCA1 plays an essential role in the formation of high-density lipoprotein (HDL), and its mutations cause Tangier disease (TD), a familial HDL deficiency. In addition to the disappearance of HDL, TD patients exhibit cholesterol deposition in peripheral tissues through a mechanism poorly understood, which may contribute to the development of premature atherosclerosis. We and others previously showed that ABCA1 deficiency causes hyperactivation of the SREBP2 pathway in vitro. Here, we show using Abca1 knockout mice that ABCA1 deficiency leads to tissue-specific dysregulation of SREBP2 activity in a nutritional status-dependent manner, which may underlie the pathophysiology of TD.

Human cytomegalovirus infection impairs neural differentiation via repressing sterol regulatory element binding protein 2-mediated cholesterol biosynthesis.

Congenital human cytomegalovirus (HCMV) infection is a major cause of abnormalities and disorders in the central nervous system (CNS) and/or the peripheral nervous system (PNS). However, the complete pathogenesis of neural differentiation disorders caused by HCMV infection remains to be fully elucidated. Stem cells from human exfoliated deciduous teeth (SHEDs) are mesenchymal stem cells (MSCs) with a high proliferation and neurogenic differentiation capacity. Since SHEDs originate from the neural crest of the early embryonic ectoderm, SHEDs were hypothesized to serve as a promising cell line for investigating the pathogenesis of neural differentiation disorders in the PNS caused by congenital HCMV infection. In this work, SHEDs were demonstrated to be fully permissive to HCMV infection and the virus was able to complete its life cycle in SHEDs. Under neurogenic inductive conditions, HCMV infection of SHEDs caused an abnormal neural morphology. The expression of stem/neural cell markers was also disturbed by HCMV infection. The impairment of neural differentiation was mainly due to a reduction of intracellular cholesterol levels caused by HCMV infection. Sterol regulatory element binding protein-2 (SREBP2) is a critical transcription regulator that guides cholesterol synthesis. HCMV infection was shown to hinder the migration of SREBP2 into nucleus and resulted in perinuclear aggregations of SREBP2 during neural differentiation. Our findings provide new insights into the prevention and treatment of nervous system diseases caused by congenital HCMV infection.

Gypenoside L inhibits hepatocellular carcinoma by targeting the SREBP2-HMGCS1 axis and enhancing immune response.

Hepatocellular carcinoma (HCC) is a malignant tumor that occurs in the liver, with a high degree of malignancy and relatively poor prognosis. Gypenoside L has inhibitory effects on liver cancer cells. However, its mechanism of action is still unclear. This study aims to investigate the inhibitory effects of gypenoside L on HCC in vitro and in vivo, and explore its potential mechanisms. The results showed that gypenoside L reduced the cholesterol and triglyceride content in HepG2 and Huh-7 cells, inhibited cell proliferation, invasion and metastasis, arrested cell cycle at G0/G1 phase, promoted cell apoptosis. Mechanistically, it targeted the transcription factor SREPB2 to inhibit the expression of HMGCS1 protein and inhibited the downstream proteins HMGCR and MVK, thereby regulating the mevalonate (MVA) pathway. Overexpression HMGCS1 led to significant alterations in the cholesterol metabolism pathway of HCC, which mediated HCC cell proliferation and conferred resistance to the therapeutic effect of gypenoside L. In vivo, gypenoside L effectively suppressed HCC growth in tumor-bearing mice by reducing cholesterol production, exhibiting favorable safety profiles and minimal toxic side effects. Gypenoside L modulated cholesterol homeostasis, enhanced expression of inflammatory factors by regulating MHC I pathway-related proteins to augment anticancer immune responses. Clinical samples from HCC patients also exhibited high expression levels of MVA pathway-related genes in tumor tissues. These findings highlight gypenoside L as a promising agent for targeting cholesterol metabolism in HCC while emphasizing the effectiveness of regulating the SREBP2-HMGCS1 axis as a therapeutic strategy.

LY86 facilitates ox-LDL-induced lipid accumulation in macrophages by upregulating SREBP2/HMGCR expression.

LY86, also known as MD1, has been implicated in various pathophysiological processes including inflammation, obesity, insulin resistance, and immunoregulation. However, the role of LY86 in cholesterol metabolism remains incompletely understood. Several studies have reported significant up-regulation of LY86 mRNA in atherosclerosis; nevertheless, the regulatory mechanism by which LY86 is involved in this disease remains unclear. In this study, we aimed to investigate whether LY86 affects ox-LDL-induced lipid accumulation in macrophages. Firstly, we confirmed that LY86 is indeed involved in the process of atherosclerosis and found high expression levels of LY86 in human atherosclerotic plaque tissue. Furthermore, our findings suggest that LY86 may mediate intracellular lipid accumulation induced by ox-LDL through the SREBP2/HMGCR pathway. This mechanism could be associated with increased cholesterol synthesis resulting from enhanced endoplasmic reticulum stress response.

The impact of sericin on inflammation, oxidative stress, and lipid metabolism in female rats with experimental knee osteoarthritis.

OBJECTIVE: This study investigated the effects of sericin on inflammation, oxidative stress, and lipid metabolism in female rats with experimental knee osteoarthritis (KOA), focusing on evaluating its effectiveness via the sterol regulatory protein (SREBP)-1C and SREBP-2 pathways. METHODS: The rats were randomly assigned to three experimental groups: the C group (control), the KOA group (KOA control), and the sericin group (KOA + sericin). The KOA model was created by injecting monosodium iodoacetate (MIA) into the knee joint. Sericin was administered intra-articularly to rats on days 1, 7, 14, and 21 (0.8 g/kg/mL, 50 µL). After 21 days, the rats were sacrificed, and serum samples were analyzed using an ELISA to measure tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1ß), IL-10, SREBP-1c, SREBP-2, acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), cholesterol, triglyceride, and total oxidant-antioxidant status (TOS-TAS) levels. RESULTS: The KOA group exhibited higher serum TNF-α, IL-1ß, TOS, SREBP-1C, ACC, FAS, triglyceride, SREBP-2, and cholesterol levels than the C group (P < 0.05). However, the levels of these cytokines, except cholesterol, were significantly lower in the sericin group than in the KOA group. The KOA group exhibited significantly lower serum TAS and IL-10 levels than the C group (P < 0.05). In the sericin group, there was a statistically significant increase (P < 0.05). CONCLUSION: Sericin shows promising potential for reducing inflammation, oxidative stress, and lipid metabolism in experimental models of KOA in rats. However, further clinical research is necessary to validate the potential of sericin as a therapeutic agent for treating KOA. Key Points • Sericin can reduce knee osteoarthritis (KOA) symptoms in an experimental rat model. • In particular, in the serum of an experimental KOA rat model, sericin specifically reduces the levels of proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α) and interleukin-1beta (IL-1ß), and increases the levels of anti-inflammatory cytokines, such as IL-10. • Sericin reduced lipid metabolism via the sterol regulatory protein (SREBP)-1C and SREBP-2 pathways and oxidative stress in the serum of the experimental KOA rat model. • The intra-articular administration of sericin has been shown to significantly reduce lipid metabolism, oxidative stress, and inflammation, as supported by biochemical analysis. These findings suggest its promising potential as an alternative treatment option for KOA.

Hawthorn leaf flavonoids alleviate the deterioration of atherosclerosis by inhibiting SCAP-SREBP2-LDLR pathway through sPLA2-â ¡A signaling in macrophages in mice.

ETHNOPHARMACOLOGICAL RELEVANCE: Hawthorn leaves are a combination of the dried leaves of the Rosaceae plants, i.e., Crataegus pinnatifida Bge. or Crataegus pinnatifida Bge. var. major N. E. Br., is primarily cultivated in East Asia, North America, and Europe. hawthorn leaf flavonoids (HLF) are the main part of extraction. The HLF have demonstrated potential in preventing hypertension, inflammation, hyperlipidemia, and atherosclerosis. However, the potential pharmacological mechanism behind its anti-atherosclerotic effect has yet to be explored. AIM OF THE STUDY: The in vivo and in vitro effects of HLF on lipid-mediated foam cell formation were investigated, with a specific focus on the levels of secreted phospholipase A2 type IIA (sPLA2-II A) in macrophage cells. MATERIALS AND METHODS: The primary constituents of HLF were analyzed using ultra-high performance liquid chromatography and liquid chromatography-tandem mass spectrometry. In vivo, HLF, at concentrations of 5 mg/kg, 20 mg/kg, and 40 mg/kg, were administered to apolipoprotein E knockout mice (ApoE-/-) fed by high-fat diet (HFD) for 16 weeks. Aorta and serum samples were collected to identify lesion areas and lipids through mass spectrometry analysis to dissect the pathological process. RAW264.7 cells were incubated with oxidized low-density lipoprotein (ox-LDL) alone, or ox-LDL combined with different doses of HLF (100, 50, and 25 µg/ml), or ox-LDL plus 24-h sPLA2-IIA inhibitors, for cell biology analysis. Lipids and inflammatory cytokines were detected using biochemical analyzers and ELISA, while plaque size and collagen content of plaque were assessed by HE and the Masson staining of the aorta. The lipid deposition in macrophages was observed by Oil Red O staining. The expression of sPLA2-IIA and SCAP-SREBP2-LDLR was determined by RT-qPCR and Western blot analysis. RESULTS: The chemical profile of HLF was studied using UPLC-Q-TOF-MS/MS, allowing the tentative identification of 20 compounds, comprising 1 phenolic acid, 9 flavonols and 10 flavones, including isovitexin, vitexin-4″-O-glucoside, quercetin-3-O-robibioside, rutin, vitexin-2″-O-rhamnoside, quercetin, etc. HLF decreased total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and non-high-density lipoprotein cholesterol (non-HDL-C) levels in ApoE-/- mice (P < 0.05), reduced ox-LDL uptake, inhibited level of inflammatory factors, such as IL-6, IL-8, TNF-α, and IL-1ꞵ (P < 0.001), and alleviated aortic plaques with a thicker fibrous cap. HLF effectively attenuated foam cell formation in ox-LDL-treated RAW264.7 macrophages, and reduced levels of intracellular TC, free cholesterol (FC), cholesteryl ester (CE), IL-6, TNF-α, and IL-1ß (P < 0.001). In both in vivo and in vitro experiments, HLF significantly downregulated the expression of sPLA2-IIA, SCAP, SREBP2, LDLR, HMGCR, and LOX-1 (P < 0.05). Furthermore, sPLA2-IIA inhibitor effectively mitigated inflammatory release in RAW264.7 macrophages and regulated SCAP-SREBP2-LDLR signaling pathway by inhibiting sPLA2-IIA secretion (P < 0.05). CONCLUSION: HLF exerted a protective effect against atherosclerosis through inhibiting sPLA2-IIA to diminish SCAP-SREBP2-LDLR signaling pathway, to reduce LDL uptake caused foam cell formation, and to slow down the progression of atherosclerosis in mice.

Cholesterol-regulated cellular stiffness may enhance evasion of NK cell-mediated cytotoxicity in gastric cancer stem cells.

Gastric cancer has a high rate of recurrence, and as such, immunotherapy strategies are being investigated as a potential therapeutic strategy. Although the involvement of immune checkpoints in immunotherapy is well studied, biomechanical cues, such as target cell stiffness, have not yet been subject to the same level of investigation. Changes in the cholesterol content of the cell membrane directly influence tumor cell stiffness. Here, we investigated the effect of cholesterol on NK cell-mediated killing of gastric cancer stem-like cells. We report that surviving tumor cells with stem-like properties elevated cholesterol metabolism to evade NK cell cytotoxicity. Inhibition of cholesterol metabolism enhances NK cell-mediated killing of gastric cancer stem-like cells, highlighting a potential avenue for improving immunotherapy efficacy. This study suggests a possible effect of cancer cell stiffness on immune evasion and offers insights into enhancing immunotherapeutic strategies against tumors.

[Ginsenoside F1 inhibits cholesterol overload in oxidative-damaged cells through SREBP2/HMGCR pathway].

OBJECTIVE: To investigate the inhibitory mechanisms of ginsenoside F1 on hydrogen peroxide induced cholesterol metabolism disorder and oxidative stress in HepG2 cells. METHODS: 1, 1-diphenyl-2-picrylhydrazyl(DPPH) and oxygen radical absorbance capacity(ORAC) tests were used to detect the scavenging effect of ginsenoside F1 on nitrogen and oxygen free radicals. HepG2 cells were treated with 400 µmol/L hydrogen peroxide and pretreated with 10, 20 and 40 µmol/L ginsenoside F1. Mitochondrial membrane potential(MMP) and total cholesterol levels were detected by JC-1 method and cholesterol kit, respectively. The protein expression levels of sterol-regulatory element binding proteins(SREBP2)and 3-hydroxy-3-methylglutaryl coenzyme A reductase(HMGCR) in cholesterol synthesis pathway were detected by Western blot. RESULTS: The DPPH clearance rate of ginsenoside F1 was much lower than that of 6-hydroxy-2, 5, 7, 8-tetramethylchroman-2-carboxylic acid(Trolox), but the ORAC capability of ginsenoside F1 was stronger, which was comparable to Trolox. The MMP and protein expression of SREBP2 were significantly decreased in injured group(P<0.05). The cholesterol and protein expression of HMGCR were significantly increased(P<0.05). Whereas, compared with the injured group, the MMP and protein expression of SREBP2 were significantly increased after 10, 20 and 40 µmol/L ginsenoside F1 pretreatment of injured cells(P<0.05). The cholesterol level and protein expression of HMGCR were significantly lower than injured group with concentration-dependent decreases(P<0.05). CONCLUSION: Ginsenoside F1 can protect against hydrogen peroxide induced oxidative stress in HepG2 cells by inhibiting oxygen free radicals and protecting mitochondria. And its mechanism may be related to the intervention of SREBP2/HMGCR pathway in regulating cellular cholesterol anabolism.