Targeting PPARs for therapy of atherosclerosis: A review

Huoxue Tongluo tablet enhances atherosclerosis efferocytosis by promoting the differentiation of Trem2+ macrophages via PPARγ signaling pathway

BACKGROUND

Atherosclerosis (AS) serves as the primary pathological basis for various cardiovascular and cerebrovascular diseases. Impaired efferocytosis by macrophages within AS plaques exacerbates lipid metabolism disorders and inflammatory responses. Huoxue Tongluo Tablet (HXTL), a traditional Chinese medicine formula, has shown efficacy in treating AS and modulating macrophage function. However, its underlying mechanisms remain unclear. It is hypothesized that HXTL ameliorates AS by enhancing macrophage efferocytosis.

PURPOSE

To assess the efficacy and mechanisms of HXTL in treating AS at the single-cell level.

METHODS

Ultra-high-performance liquid chromatography-mass spectrometry (UPLC-MS/MS) was used to analyze the constituents of HXTL. HXTL was administered to ApoE⁻/⁻ mice maintained on a high-fat diet. The progression of AS was evaluated by measuring atherosclerotic plaque area, necrotic core formation, collagen depletion, lipid accumulation, lipid profiles, pro-inflammatory mediators, and oxidative stress markers. Transcriptomic analysis was performed to explore the mechanisms underlying the therapeutic effects of HXTL on AS. Efferocytosis-related marker expression was evaluated using immunohistochemistry and quantitative PCR (qPCR), and the efferocytosis index was determined by the co-localization of apoptotic cells and macrophages. Efferocytosis inhibition was induced using Cytochalasin D. Single-cell sequencing was utilized to investigate alterations in Trem2⁺ macrophages following HXTL treatment. Trem2 expression was accessed by immunohistochemistry and qPCR, while flow cytometry and immunofluorescence staining confirmed the changes in Trem2⁺ macrophages. Bioinformatic analyses were conducted to investigate the mechanism through which HXTL enhances efferocytosis by regulating Trem2⁺ macrophage subsets. Western blotting and qPCR were used to assess the expression levels of PPARγ signaling, and the regulatory role of PPARγ signaling in macrophage subpopulation generation and efferocytosis function was accessed using GW9662.

RESULTS

UPLC-MS/MS analysis identified 99 major components in HXTL. In vivo, medium and high doses of HXTL significantly reduced atherosclerotic plaque area, improved lipid profiles, decreased pro-inflammatory mediators and reactive oxygen species (ROS), and enhanced the efferocytosis function. Inhibition of efferocytosis reversed these beneficial effects. Single-cell sequencing and in vivo validation revealed that HXTL upregulated Trem2⁺ macrophages and efferocytosis-related genes. Bioinformatics and in vivo experiments demonstrated that HXTL activated PPARγ signaling, and inhibition of PPARγ signaling negated the pro-efferocytosis effects and the upregulation of Trem2⁺ macrophage upregulation induced by HXTL.

CONCLUSIONS

HXTL activates the PPARγ pathway, upregulates Trem2⁺ macrophages, and enhances macrophage efferocytosis, thereby ameliorating AS. This study is the first to demonstrate the regulatory effects of HXTL on macrophage subpopulations and its pro-efferocytosis activity.

Integrative analysis of genes provides insights into the molecular and immune characteristics of mitochondria-related genes in atherosclerosis

Atherosclerosis is a chronic inflammatory disease characterized by lipid accumulation in arterial walls. The role of the interplay between mitochondrial dysfunction and immune inflammation in atherosclerosis is still unclear. This study aimed to investigate the molecular characteristics and immune landscape of mitochondrial hub genes involved in atherosclerosis. Based on bioinformatics analysis, three hub Mitochondria-related DEGs (MitoDEGs), including OXCT1, UCP2, and CPT1B, were screened out and showed good diagnostic performance in identifying atherosclerosis patients and controls. Immune analysis demonstrated strong correlations between hub MitoDEGs and immune cells, such as macrophages and T cells. Additionally, the predicted transcription factors of these hub MitoDEGs were significantly enriched in Th17, Th1 and Th2 cell differentiation signaling pathways. Both cell and animal experiments confirmed the expression trends of OXCT1 and CPT1B observed in the bioinformatics analysis. These hub MitoDEGs may play an important role in coordinating mitochondrial metabolism in the immune inflammation of atherosclerosis.

PPARs in atherosclerosis: The spatial and temporal features from mechanism to druggable targets

BACKGROUND

Atherosclerosis is a chronic and complex disease caused by lipid disorder, inflammation, and other factors. It is closely related to cardiovascular diseases, the chief cause of death globally. Peroxisome proliferator-activated receptors (PPARs) are valuable anti-atherosclerosis targets that showcase multiple roles at different pathological stages of atherosclerosis and for cell types at different tissue sites.

AIM OF REVIEW

Considering the spatial and temporal characteristics of the pathological evolution of atherosclerosis, the roles and pharmacological and clinical studies of PPARs were summarized systematically and updated under different pathological stages and in different vascular cells of atherosclerosis. Moreover, selective PPAR modulators and PPAR-pan agonists can exert their synergistic effects meanwhile reducing the side effects, thereby providing novel insight into future drug development for precise spatial-temporal therapeutic strategy of anti-atherosclerosis targeting PPARs.

KEY SCIENTIFIC

Concepts of Review: Based on the spatial and temporal characteristics of atherosclerosis, we have proposed the importance of stage- and cell type-dependent precision therapy. Initially, PPARs improve endothelial cells' dysfunction by inhibiting inflammation and oxidative stress and then regulate macrophages' lipid metabolism and polarization to improve fatty streak. Finally, PPARs reduce fibrous cap formation by suppressing the proliferation and migration of vascular smooth muscle cells (VSMCs). Therefore, research on the cell type-specific mechanisms of PPARs can provide the foundation for space-time drug treatment. Moreover, pharmacological studies have demonstrated that several drugs or compounds can exert their effects by the activation of PPARs. Selective PPAR modulators (that specifically activate gene subsets of PPARs) can exert tissue and cell-specific effects. Furthermore, the dual- or pan-PPAR agonist could perform a better role in balancing efficacy and side effects. Therefore, research on cells/tissue-specific activation of PPARs and PPAR-pan agonists can provide the basis for precision therapy and drug development of PPARs.

Anti-atherosclerotic effects of natural compounds targeting lipid metabolism and inflammation: Focus on PPARs, LXRs, and PCSK9

A large body of evidence has shown that modulation of the nuclear receptors peroxisome proliferator-activated receptors (PPARs), the liver X receptors (LXRs), the proprotein convertase subtilisin/kexin type 9 (PCSK9) and inflammatory processes by natural compounds has hypolipidemic and anti-atherosclerotic effects. These beneficial outcomes are certainly related to the crucial function of these targets in maintaining cholesterol homeostasis and regulating systemic inflammation. Currently, the therapeutic scenario for cardiovascular diseases (CVD) offers a plethora of widely validated and functional pharmacological treatments to improve the health status of patients. However, patients are increasingly sceptical of pharmacological treatments which are often associated with moderate to severe side effects. The aim of our review is to provide a collection of the most recent scientific evidence on the most common phytochemicals, used for centuries in the Mediterranean diet and traditional chinese medicine that act on these key regulators of cholesterol homeostasis and systemic inflammation, which could constitute important tools for CVD management.

Conditional knockdown of hepatic PCSK9 ameliorates high-fat diet-induced liver inflammation in mice

Instruction

Accumulating evidence has shown that proprotein convertase subtilisin/kexin type 9 (PCSK9) is associated with inflammation in the vascular system. However, the roles of PCSK9 in hepatic inflammation remain unclear. Because PCSK9 is mainly expressed in the liver and modulates lipid uptake through low-density lipoprotein receptor family members, the present study aimed to elucidate the effect of conditional knockdown of hepatic PCSK9 on hyperlipidemia-induced inflammation and the underlying mechanisms of action.

Methods

PCSK9flox/flox mice were bred with ALB-Cre+ mice to obtain hepatic PCSK9 (-/-) , PCSK9 (+/-) , and PCSK9 (+/+) mice. These mice were fed with a high-fat diet for 9 weeks to induce inflammation. The effects of conditional knockdown of hepatic PCSK9 on inflammation and the underlying mechanisms were investigated by molecular biological techniques. Moreover, the findings were verified in vitro using HepG2 cells.

Results and Discussion

Conditional knockdown of hepatic PCSK9 remarkably decreased plasma levels of total cholesterol and alleviated hyperlipidemia-induced liver injury. Mechanistically, conditional knockdown of hepatic PCSK9 significantly reduced the levels of pro-inflammatory factors by downregulating the expression of Toll-like receptors, mitogen-activated protein kinase (MAPK), and phosphoinositide-3 kinase/protein kinase B, which subsequently attenuated the expression of downstream molecules, namely nuclear factor kappa-B and activator protein-1. The related mechanisms were confirmed using lipid-loaded HepG2 cells together with PCSK9 siRNA, alirocumab (anti-PCSK9 antibody), and/or a p38-MAPK inhibitor. These findings confirmed that conditional knockdown of hepatic PCSK9 attenuates liver inflammation following hyperlipidemia induction by modulating multiple signaling pathways; this suggests that targeting PCSK9 knockdown/inhibition with appropriate agents is useful not only for treating hyperlipidemia but also for ameliorating hyperlipidemia-induced liver inflammation.

Cajaninstilbene Acid and Its Derivative as Multi-Therapeutic Agents: A Comprehensive Review

Pigeon pea (Cajanus cajan (L.) Millsp.) is a traditional Chinese medicinal plant widely utilized in folk medicine due to its significant pharmacological and nutritional properties. Cajaninstilbene acid (CSA), a stilbene compound derived from pigeon pea leaves, has been extensively investigated since the 1980s. A thorough understanding of CSA's mechanisms of action and its therapeutic effects on various diseases is crucial for developing novel therapeutic approaches. This paper presents an overview of recent research advancements concerning the biological activities and mechanisms of CSA and its derivatives up to February 2024. The review encompasses discussions on the in vivo metabolism of CSA and its derivatives, including antipathogenic micro-organisms activity, anti-tumor activity, systematic and organ protection activity (such as bone protection, cardiovascular protection, neuroprotection), anti-inflammatory activity, antioxidant activity, immune regulation as well as action mechanism of CSA and its derivatives. The most studied activities are antipathogenic micro-organisms activities. Additionally, the structure-activity relationships of CSA and its derivatives as well as the total synthesis of CSA are explored, highlighting the potential for developing new pharmaceutical agents. This review aims to provide a foundation for future clinical applications of CSA and its derivatives.

Chondroitin sulfate functionalized nanozymes inhibit the inflammation feedback loop for enhanced atherosclerosis therapy by regulating intercellular crosstalk

In the inflammatory microenvironment of atherosclerotic plaques, metabolic dysregulation of superoxide anion (O2-) and hydrogen peroxide (H2O2) leads to the activation of feedback mechanisms involving IL-1β, TNF-α, and MCP-1, which triggers inflammatory cascades between macrophages and vascular smooth muscle cells (VSMCs) in atherosclerosis (AS). To address this, a chondroitin sulfate (CS)-functionalized dual-targeted engineered nanozyme, CS-Lip/PB@Rap, was developed by encapsulating mesoporous Prussian blue nanoparticles (PBs) loaded with rapamycin (Rap) within CS-modified liposomes. CS functionalization endowed CS-Lip/PB@Rap with a specific targeting ability for CD44 receptors, thus enabling targeted delivery to inflammatory macrophages and VSMCs. Moreover, its enhanced multiple enzyme-like activities effectively modulated the imbalance of oxidative stress. The underlying mechanism of crosstalk regulation by these engineered nanozymes may inhibit the NF-κB pathway by restoring normal metabolism of O2- and H2O2, thereby blocking the TNF-α, IL-1β, and MCP-1 feedback loops between macrophages and VSMCs. This process reduced the production of inflammatory macrophages and inhibited the VSMC transformation from a contractile phenotype to a synthetic phenotype, preventing the formation of fibrous caps. Furthermore, the elimination of oxidative stress could decrease the production of oxygenized low-density lipoprotein (ox-LDL), which inhibited the formation of foam cells and alleviated the atherogenic progression.

Overview of multifunctional Tregs in cardiovascular disease: From insights into cellular functions to clinical implications

Regulatory T cells (Tregs) are crucial in regulating T-cell-mediated immune responses. Numerous studies have shown that dysfunction or decreased numbers of Tregs may be involved in inflammatory cardiovascular diseases (CVDs) such as atherosclerosis, hypertension, myocardial infarction, myocarditis, cardiomyopathy, valvular heart diseases, heart failure, and abdominal aortic aneurysm. Tregs can help to ameliorate CVDs by suppressing excessive inflammation through various mechanisms, including inhibition of T cells and B cells, inhibition of macrophage-induced inflammation, inhibition of dendritic cells and foam cell formation, and induction of anti-inflammatory macrophages. Enhancing or restoring the immunosuppressive activity of Tregs may thus serve as a fundamental immunotherapy to treat hypertension and CVDs. However, the precise molecular mechanisms underlying the Tregs-induced protection against hypertension and CVDs remain to be investigated. This review focuses on recent advances in our understanding of Tregs subsets and function in CVDs. In addition, we discuss promising strategies for using Tregs through various pharmacological approaches to treat hypertension and CVDs.

Exserolide J ameliorates lipid accumulation in vitro by regulating liver X receptor alpha and peroxisome proliferator-activated receptor alpha proteins

Exserolides are isocoumarin derivatives containing lactone moiety. Recently, some isocoumarins have been demonstrated to ameliorate hyperlipidemia, a major factor for inducing cardiovascular diseases. However, the effects and mechanisms of action of exserolides on hyperlipidemia are not known. The aim of this study is to investigate whether the marine fungus Setosphaeria sp.-derived exserolides (compounds I, J, E, and F) exert lipid-lowering effects via improving reverse cholesterol transport (RCT) in vitro. RAW264.7 macrophages and HepG2 cells were used to establish lipid-laden models, and the levels of intracellular lipids and RCT-related proteins were determined by assay kits and Western blotting, respectively. We observed that exserolides (at a 5 μM concentration) significantly decreased intracellular cholesterol and triglyceride levels in oxidized low-density lipoprotein-laden RAW264.7 cells and markedly improved [3H]-cholesterol efflux. Among the four tested compounds, exserolide J increased the protein levels of ATP-binding cassette transporter A1, peroxisome proliferator-activated receptor α (PPARα), and liver X receptor α (LXRα). Furthermore, treatment with exserolides significantly decreased oleic acid-laden lipid accumulation in HepG2 hepatocytes. Mechanistically, exserolides enhance PPARα protein levels; furthermore, compound J increases cholesterol 7 alpha-hydroxylase A1 and LXRα protein levels. Molecular docking revealed that exserolides, particularly compound J, can interact with PPARα and LXRα proteins. These data suggest that the terminal carboxyl group of compound J plays a key role in lowering lipid levels by stimulating LXRα and PPARα proteins. In conclusion, compound J exhibits powerful lipid-lowering effects in vitro. However, its hypolipidemic effects in vivo should be investigated in the future.

A comparative study of the hypolipidemic effects and mechanisms of action of Laminaria japonica- and Ascophyllum nodosum-derived fucoidans in apolipoprotein E-deficient mice

The structural characteristics of fucoidans exhibit species and regional diversity. Previous studies have demonstrated that Laminaria japonica- and Ascophyllum nodosum-derived fucoidans have type I and type II fucosyl chains, respectively. These chemical differences may contribute to distinct hypolipidemic effects and mechanisms of action. Chemical analysis demonstrated that the percentage contents of sulfate, glucuronic acid, and galactose were higher in L. japonica-derived fucoidans than those of A. nodosum-derived fucoidans. In hyperlipidemic apolipoprotein E-deficient mice, both A. nodosum- and L. japonica-derived fucoidans significantly decreased the plasma and hepatic levels of total cholesterol and triglyceride, leading to the reduction of atherosclerotic plaques. Western blotting experiments demonstrated that these fucoidans significantly enhanced the expression and levels of scavenger receptor B type 1, cholesterol 7 alpha-hydroxylase A1, and peroxisome proliferator-activated receptor (PPAR)-α, contributing to circulating lipoprotein clearance and fatty acid degradation, respectively. Differentially, L. japonica-derived fucoidan significantly increased the LXR/ATP-binding cassette G8 signaling pathway in the small intestine, as revealed by real-time quantitative PCR, which may lead to further cholesterol and other lipid excretion. Collectively, these data are useful for understanding the hypolipidemic mechanisms of action of seaweed-derived fucoidans, and their potential application for the prevention and/or treatment of atherosclerotic cardiovascular diseases.

Natural products in atherosclerosis therapy by targeting PPARs: a review focusing on lipid metabolism and inflammation

Inflammation and dyslipidemia are critical inducing factors of atherosclerosis. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors and control the expression of multiple genes that are involved in lipid metabolism and inflammatory responses. However, synthesized PPAR agonists exhibit contrary therapeutic effects and various side effects in atherosclerosis therapy. Natural products are structural diversity and have a good safety. Recent studies find that natural herbs and compounds exhibit attractive therapeutic effects on atherosclerosis by alleviating hyperlipidemia and inflammation through modulation of PPARs. Importantly, the preparation of natural products generally causes significantly lower environmental pollution compared to that of synthesized chemical compounds. Therefore, it is interesting to discover novel PPAR modulator and develop alternative strategies for atherosclerosis therapy based on natural herbs and compounds. This article reviews recent findings, mainly from the year of 2020 to present, about the roles of natural herbs and compounds in regulation of PPARs and their therapeutic effects on atherosclerosis. This article provides alternative strategies and theoretical basis for atherosclerosis therapy using natural herbs and compounds by targeting PPARs, and offers valuable information for researchers that are interested in developing novel PPAR modulators.

Laminaria japonica Aresch-Derived Fucoidan Ameliorates Hyperlipidemia by Upregulating LXRs and Suppressing SREBPs

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality worldwide, and hyperlipidemia is one major inducing factor of CVD. It is worthy to note that fucoidans are reported to have hypolipidemic activity with species specificity; however, the underlying mechanisms of action are far from clarification. This study is aimed at investigating the plasma lipid-lowering mechanisms of the fucoidan from L. japonica Aresch by detecting the levels of hepatic genes that are involved in lipid metabolism. Our results demonstrated that the fucoidan F3 significantly lowered total cholesterol and triglyceride in C57BL/6J mice fed a high-fat diet. In the mouse liver, fucoidan F3 intervention significantly increased the gene expression of peroxisome proliferator-activated receptor (PPAR) α, liver X receptor (LXR) α and β, and ATP-binding cassette transporter (ABC) G1 and G8 and decreased the expression of proprotein convertase subtilisin/kexin type 9 (PCSK9), low-density lipoprotein receptor, cholesterol 7 alpha-hydroxylase A1, and sterol regulatory element-binding protein (SREBP) 1c and SREBP-2. These results demonstrated that the antihyperlipidemic effects of fucoidan F3 are related to its activation of PPARα and LXR/ABC signaling pathways and inactivation of SREBPs. In conclusion, fucoidan F3 may be explored as a potential compound for prevention or treatment of lipid disorders.

Peroxisome proliferator-activated receptors: A key link between lipid metabolism and cancer progression

Lipids represent the essential components of membranes, serve as fuels for high-energy processes, and play crucial roles in signaling and cellular function. One of the key hallmarks of cancer is the reprogramming of metabolic pathways, especially abnormal lipid metabolism. Alterations in lipid uptake, lipid desaturation, de novo lipogenesis, lipid droplets, and fatty acid oxidation in cancer cells all contribute to cell survival in a changing microenvironment by regulating feedforward oncogenic signals, key oncogenic functions, oxidative and other stresses, immune responses, or intercellular communication. Peroxisome proliferator-activated receptors (PPARs) are transcription factors activated by fatty acids and act as core lipid sensors involved in the regulation of lipid homeostasis and cell fate. In addition to regulating whole-body energy homeostasis in physiological states, PPARs play a key role in lipid metabolism in cancer, which is receiving increasing research attention, especially the fundamental molecular mechanisms and cancer therapies targeting PPARs. In this review, we discuss how cancer cells alter metabolic patterns and regulate lipid metabolism to promote their own survival and progression through PPARs. Finally, we discuss potential therapeutic strategies for targeting PPARs in cancer based on recent studies from the last five years.

M6A plays a potential role in carotid atherosclerosis by modulating immune cell modification and regulating aging-related genes

RNA N6-methyladenosine (m6A) regulators play essential roles in diverse biological processes, including immune responses. Mounting evidence suggests that their dysregulation is intricately linked to numerous diseases. However, the role of m6A-associated genes in carotid atherosclerosis and their relationship with aging and immune cells remain unclear. Analyze the expression profiles of m6A-related genes in carotid atherosclerosis-related datasets. Based on the expression patterns of m6A-related genes, perform consistent clustering analysis of carotid atherosclerosis samples and investigate associated immune cell infiltration patterns and aging characteristics. Develop an m6A prediction model specific to carotid atherosclerosis and analyze the relationships between immune cells infiltration and aging features. The m6A methylation modification level exhibited a substantial decrease in early-stage carotid atherosclerosis samples compared to late-stage carotid atherosclerosis samples. Subsequently, two distinct m6A subtypes were defined through consensus clustering analysis, with the lower m6A modification level group showing associations with heightened immune cell infiltration and increased expression of aging-related genes. A model composed of five m6A-related genes was formulated, and the results indicated that this model possesses effective predictive and therapeutic capabilities for carotid atherosclerosis. Furthermore, the downregulation of YTHDC1 expression resulted in elevated expression of inflammatory factors and a decrease in the expression of the aging-related gene RGN. Single-cell data analysis suggests that the reduced expression of YTHDC1 may decrease the degradation of inflammation-related factors in macrophages, leading to a highly inflammatory state in the carotid artery wall. Furthermore, the sustained release of inflammatory factors may increase the expression of the aging-related gene RGN in vascular smooth muscle cells, further exacerbating the progression of atherosclerosis. A reduced level of m6A methylation modification could enhance inflammation and expedite cellular aging, thereby contributing to the development of carotid atherosclerosis.

Essential oil from Fructus Alpinia zerumbet ameliorates atherosclerosis by activating PPARγ-LXRα-ABCA1/G1 signaling pathway

BACKGROUND

Atherosclerosis (AS) is a progressive chronic disease. Currently, cardiovascular diseases (CVDs) caused by AS is responsible for the global increased mortality. Yanshanjiang as miao herb in Guizhou of China is the dried and ripe fruit of Fructus Alpinia zerumbet. Accumulated evidences have confirmed that Yanshanjiang could ameliorate CVDs, including AS. Nevertheless, its effect and mechanism on AS are still largely unknown.

PURPOSE

To investigate the role of essential oil from Fructus Alpinia zerumbet (EOFAZ) on AS, and the potential mechanism.

METHODS

A high-fat diet (HFD) ApoE-/- mice model of AS and a oxLDL-induced model of macrophage-derived foam cells (MFCs) were reproduced to investigate the pharmacological properties of EOFAZ on AS in vivo and foam cell formation in vitro, respectively. The underlying mechanisms of EOFAZ were investigated using Network pharmacology and molecular docking. EOFAZ effect on PPARγ protein stability was measured using a cellular thermal shift assay (CETSA). Pharmacological agonists and inhibitors and gene interventions were employed for clarifying EOFAZ's potential mechanism.

RESULTS

EOFAZ attenuated AS progression in HFD ApoE-/- mice. This attenuation was manifested by the reduced aortic intima plaque development, increased collagen content in aortic plaques, notable improvement in lipid profiles, and decreased levels of inflammatory factors. Moreover, EOFAZ inhibited the formation of MFCs by enhancing cholesterol efflux through activiting the PPARγ-LXRα-ABCA1/G1 pathway. Interestingly, the pharmacological knockdown of PPARγ impaired the beneficial effects of EOFAZ on MFCs. Additionally, our results indicated that EOFAZ reduced the ubiquitination degradation of PPARγ, and the chemical composition of EOFAZ directly bound to the PPARγ protein, thereby increasing its stability. Finally, PPARγ knockdown mitigated the protective effects of EOFAZ on AS in HFD ApoE-/- mice.

CONCLUSION

These findings represent the first confirmation of EOFAZ's in vivo anti-atherosclerotic effects in ApoE-/- mice. Mechanistically, its chemical constituents can directly bind to PPARγ protein, enhancing its stability, while reducing PPARγ ubiquitination degradation, thereby inhibiting foam cell formation via activation of the PPARγ-LXRα-ABCA1/G1 pathway. Simultaneously, EOFAZ could ameliorates blood lipid metabolism and inflammatory microenvironment, thus synergistically exerting its anti-atherosclerotic effects.

ACSM5 inhibits ligamentum flavum hypertrophy by regulating lipid accumulation mediated by FABP4/PPAR signaling pathway

BACKGROUND

Ligamentum flavum (LF) hypertrophy is the main cause of lumbar spinal canal stenosis (LSCS). Previous studies have shown that LF hypertrophy tissue exhibits abnormal lipid accumulation, but the regulatory mechanism remains unclear. The objective of this study was to explore the function and potential mechanism of ACSM5 in LF lipid accumulation.

METHODS

To assess the ACSM5 expression levels, lipid accumulation and triglyceride (TG) level in LF hypertrophy and normal tissue, we utilized RT-qPCR, western blot, oil red O staining, and TG assay kit. The pearson correlation coefficient assay was used to analyze the correlation between ACSM5 levels and lipid accumulation or TG levels in LF hypertrophy tissue. The role of ACSM5 in free fatty acids (FFA)-induced lipid accumulation in LF cells was assessed in vitro, and the role of ACSM5 in LF hypertrophy in mice was verified in vivo. To investigate the underlying mechanisms of ACSM5 regulating lipid accumulation in LF, we conducted the mRNA sequencing, bioinformatics analysis, and rescue experiments.

RESULTS

In this study, we found that ACSM5, which was significantly down-regulated in LF tissues, correlated with lipid accumulation. In vitro cell experiments demonstrated that overexpression of ACSM5 significantly inhibited FFA-induced lipid accumulation and fibrosis in LF cells. In vivo animal experiments further confirmed that overexpression of ACSM5 inhibited LF thickening, lipid accumulation, and fibrosis. Mechanistically, ACSM5 inhibited lipid accumulation of LF cells by inhibiting FABP4-mediated PPARγ signaling pathway, thereby improving hypertrophy and fibrosis of LF.

CONCLUSIONS

our findings elucidated the important role of ACSM5 in the regulation of LF lipid accumulation and provide insight into potential therapeutic interventions for the treatment of LF hypertrophy. This study further suggested that therapeutic strategies targeting lipid deposition may be an effective potential approach to treat LF hypertrophy-induced LSCS.

Fatty acid metabolism disorders and potential therapeutic traditional Chinese medicines in cardiovascular diseases

Cardiovascular diseases are currently the primary cause of mortality in the whole world. Growing evidence indicated that the disturbances in cardiac fatty acid metabolism are crucial contributors in the development of cardiovascular diseases. The abnormal cardiac fatty acid metabolism usually leads to energy deficit, oxidative stress, excessive apoptosis, and inflammation. Targeting fatty acid metabolism has been regarded as a novel approach to the treatment of cardiovascular diseases. However, there are currently no specific drugs that regulate fatty acid metabolism to treat cardiovascular diseases. Many traditional Chinese medicines have been widely used to treat cardiovascular diseases in clinics. And modern studies have shown that they exert a cardioprotective effect by regulating the expression of key proteins involved in fatty acid metabolism, such as peroxisome proliferator-activated receptor α and carnitine palmitoyl transferase 1. Hence, we systematically reviewed the relationship between fatty acid metabolism disorders and four types of cardiovascular diseases including heart failure, coronary artery disease, cardiac hypertrophy, and diabetic cardiomyopathy. In addition, 18 extracts and eight monomer components from traditional Chinese medicines showed cardioprotective effects by restoring cardiac fatty acid metabolism. This work aims to provide a reference for the finding of novel cardioprotective agents targeting fatty acid metabolism.

Functional and Structural Insights into the Human PPARα/δ/γ Targeting Preferences of Anti-NASH Investigational Drugs, Lanifibranor, Seladelpar, and Elafibranor

No therapeutic drugs are currently available for nonalcoholic steatohepatitis (NASH) that progresses from nonalcoholic fatty liver via oxidative stress-involved pathways. Three cognate peroxisome proliferator-activated receptor (PPAR) subtypes (PPARα/δ/γ) are considered as attractive targets. Although lanifibranor (PPARα/δ/γ pan agonist) and saroglitazar (PPARα/γ dual agonist) are currently under investigation in clinical trials for NASH, the development of seladelpar (PPARδ-selective agonist), elafibranor (PPARα/δ dual agonist), and many other dual/pan agonists has been discontinued due to serious side effects or little/no efficacies. This study aimed to obtain functional and structural insights into the potency, efficacy, and selectivity against PPARα/δ/γ of three current and past anti-NASH investigational drugs: lanifibranor, seladelpar, and elafibranor. Ligand activities were evaluated by three assays to detect different facets of the PPAR activation: transactivation assay, coactivator recruitment assay, and thermal stability assay. Seven high-resolution cocrystal structures (namely, those of the PPARα/δ/γ-ligand-binding domain (LBD)-lanifibranor, PPARα/δ/γ-LBD-seladelpar, and PPARα-LBD-elafibranor) were obtained through X-ray diffraction analyses, six of which represent the first deposit in the Protein Data Bank. Lanifibranor and seladelpar were found to bind to different regions of the PPARα/δ/γ-ligand-binding pockets and activated all PPAR subtypes with different potencies and efficacies in the three assays. In contrast, elafibranor induced transactivation and coactivator recruitment (not thermal stability) of all PPAR subtypes, but the PPARδ/γ-LBD-elafibranor cocrystals were not obtained. These results illustrate the highly variable PPARα/δ/γ activation profiles and binding modes of these PPAR ligands that define their pharmacological actions.