D4F alleviates macrophage-derived foam cell apoptosis by inhibiting CD36 expression and ER stress-CHOP pathway

MicroRNA let-7g links foam cell formation and adipogenic differentiation: A key regulator of Paeonol treating atherosclerosis-osteoporosis

BACKGROUD

High comorbidity rates have been reported in patients with atherosclerosis and osteoporosis, posing a serious risk to the health and well-being of elderly patients. To improve and update clinical practice regarding the joint treatment of these two diseases, the common mechanisms of atherosclerosis and osteoporosis need to be clarified. MicroRNAs (miRNAs), are importance molecules in the pathogenesis of human diseases, including in cardiovascular and orthopedic fields. They have garnered interest as potential targets for novel therapeutic strategies. However, the key miRNAs involved in atherosclerosis and osteoporosis and their precise regulation mechanisms remain unknown. Paeonol (Pae), an active ingredient in Cortex Moutan, has shown promising results in improving both lipid and bone metabolic abnormalities. However, it is uncertain whether this agent can exert a cotherapeutic effect on atherosclerosis and osteoporosis.

OBJECTIVE

This study aimed to screen important shared miRNAs in atherosclerotic and osteoporotic complications, and explore the mechanism of the protective effects of Pae against atherosclerosis and osteoporosis in high-fat diet (HFD)-fed ApoE-/- mice.

METHODS

An experimental atherosclerosis and osteoporosis model was established in 40-week-old HFD ApoE-/- mice. Various techniques such as Oil Red O staining, HE staining and micro-CT were used to confirm the co-occurrence of these two diseases and efficacy of Pae in addition to the associated biochemical changes. Bioinformatics was used to screen key miRNAs in the atherosclerosis and osteoporosis model, and gene involvement was assessed through serum analyses, qRT-PCR, and western blot. To investigate the effect of Pae on the modulation of the miR let-7g/HMGA2/CEBPβ pathway, Raw 264.7 cells were cocultured with bone marrow mesenchymal stem cells (BMSCs) and treated with an miR let-7g mimic/inhibitor.

RESULTS

miR let-7g identified using bioinformatics was assessed to evaluate its participation in atherosclerosis-osteoporosis. Experimental analysis showed reduced miR let-7g levels in the atherosclerosis-osteoporosis mice model. Moreover, miR let-7g was required for BMSC - Raw 264.7 cell crosstalk, thereby promoting foam cell formation and adipocyte differentiation. Treatment with Pae significantly reduced plaque accumulation and foam cell number in the aorta while increasing bone density and improving trabecular bone microarchitecture in HFD ApoE-/- mice. Pae also increased the level of miR let-7g in the bloodstream of model mice. In vitro studies, Pae enhanced miR let-7g expression in BMSCs, thereby suppressing the HMGA2/CEBPβ pathway to prevent the formation of foam cells and differentiation of adipocytes induced by oxidized low-density lipoprotein (ox-LDL).

CONCLUSION

The study results suggested that miR let-7g participates in atherosclerosis -osteoporosis regulation and that Pae acts as a potential therapeutic agent for preventing atherosclerosis-osteoporosis through regulatory effects on the miR let-7g/HMGA2/CEBPβ pathway to hinder foam cell formation and adipocyte differentiation.

2-(2-Phenylethyl)chromone-enriched extract of Chinese agarwood (Aquilaria sinensis) inhibits atherosclerosis progression through endoplasmic reticulum stress-mediated CD36 expression in macrophages

ETHNOPHARMACOLOGICAL RELEVANCE

Chinese agarwood, derived from the Aquilaria sinensis (Lour.) Gilg (Thymelaeaceae), has a long history of use in Traditional Chinese Medicine for the management of cardiovascular disease. However, the specific active ingredients responsible for its impact on atherosclerosis are yet to be fully understood.

AIM OF THE STUDY

The aim of this study is to investigate the anti-atherosclerotic effectiveness of the 2-(2-phenylethyl)chromone-enriched extract derived from Chinese agarwood (CPE) through the ER stress-mediated CD36 pathway.

MATERIALS AND METHODS

To assess the effectiveness of CPE, an atherosclerotic mouse model was established using ApoE-/- mice with a high-fat diet. Then we assessed the impact of CPE on lipid accumulation in THP-1 macrophages that were exposed to oxLDL. Subsequently, the effect of CPE on the expression of CD36 and markers related to ER stress was characterized.

RESULTS

Our in vivo research confirmed that CPE effectively reduces the formation of aortic plaques in atherosclerotic ApoE-/- mice. Additionally, our in vitro study observed that CPE inhibits the uptake of oxLDL and hinders the generation of foam cells. This effect is achieved by downregulating the level of CD36 in macrophages. Furthermore, our study revealed that the increase in CD36 expression, resulting from oxLDL exposure, is governed by the activation of JNK1/2/3 signaling pathways and the initiation of ER stress.

CONCLUSION

CPE demonstrated significant efficacy to inhibit the atherosclerosis. The ER stress/P-JNK/PPARγ/CD36 signaling pathway plays critical involvement in modulating the foam cell formation in vitro and in vivo. These findings underscore the efficacy of CPE as a viable therapeutic intervention for the treatment of atherosclerosis.

Shenlian extract protected ox-LDL-loaded macrophages against ER stress by promoting LAL-LXRα mediated cholesterol flux

ETHNOPHARMACOLOGICAL RELEVANCE

Shenlian (SL) extract is consisted of extracts from Salvia miltiorrhiza Bunge and Andrographis paniculata (Burm.f.) Nees, two herbs commonly used in Chinese clinical formula to treat atherosclerosis by removing blood stasis and clearing away heat. Pharmacologically, the anti-atherosclerotic effects of these two herbs are related to unresolved inflammation and the macrophage anergy or apoptosis in lesions led by the lipid flux blockage and ER stress. However, the deeper understanding of SL extract in protecting macrophage in plaques remains unknown.

AIM OF THE STUDY

This study aimed to investigate the underlying mechanism of SL extract in protecting ER-stressed macrophages from apoptosis in atherosclerosis.

METHODS

The ApoE-/- atherosclerotic mice model and ox-LDL loaded macrophages model were established to assess the effect of SL extract on ER stress in vivo and in vitro. Key markers related to ER stress in plaque were determined by immunohistochemical staining. Proteins involved in apoptosis and ER stress in macrophages loaded by ox-LDL were assessed by Western blot. ER morphology was observed by electron microscope. Lipid flux was temporally and quantitatively depicted by Oil red staining. The LAL and LXRα were blocked by lalistat and Gsk 2033 respectively to investigate whether SL extract protected the function of macrophages by the activation of LAL-LXRα axis.

RESULTS

Our study reported that, in ApoE-/- atherosclerotic mice, SL extract effectively relieved ER stress of carotid artery plaque. In lipid-overloaded macrophage models, SL extract significantly alleviated ER stress by promoting cholesterol degradation and efflux, which finally prevented apoptosis of foam cells induced by ox-LDL. Blockage of ER stress by 4-Phenylbutyric acid (4-PBA), an inhibitor of Endoplasmic Reticulum (ER) stress, largely attenuated the protective effects of SL extract on macrophage. By utilizing the selective antagonists against both LAL and LXRα, this study further revealed that the beneficial effects of SL extract in macrophages was dependent on the proper functionalization of LAL-LXRα axis.

CONCLUSIONS

By highlighting the therapeutic significance of macrophage protection in resolving atherosclerosis inflammation, our study pharmacologically provided convincing mechanistic evidence of SL extract in the activation LAL-LXRα axis and revealed its promising potential in the promotion of cholesterol turnover and prevention of ER stress induced apoptosis in lipid-loaded macrophages.

Apolipoprotein A-I attenuates peritoneal fibrosis associated with peritoneal dialysis by inhibiting oxidative stress and inflammation

Apolipoprotein A-I (apoA-I), 90% of which is present in high-density lipoprotein (HDL), is the main constituent of HDL, has anti-inflammatory and anti-oxidant properties, and has received extensive attention in anti-atherosclerosis. Yet little is known about apoA-I 's role in peritoneal dialysis. In this study, by analyzing PD patients (n = 81), we found that decreased apoA/HDL-C ratio is significantly associated with rapid decline in peritoneal function. Further studies were performed in animal experiments to determine the ascendancy of apolipoprotein A-I mimetic peptide (D-4F) on peritoneum, we found that D-4F administration reduced peritoneal fibrosis and peritoneal endothelial mesenchymal transformation (EMT) induced by high glucose peritoneal dialysate, such as N-cadherin, Fibronectin, Vimentin, and α-smooth muscle actin (α-SMA) expression decreased. In mechanism, D-4F can significantly inhibit Smad2/3 phosphorylation, which is the major pathway leading to fibrosis. Furthermore, D-4F treatment inhibited NADPH oxidase and thiobarbituric acid reactive substances (TBARS) expression, increased the activity of certain enzymes, such as superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). Finally, treatment with D-4F inhibits the expression of interleukins-6(IL-6), Interleukin-1β(IL-1β), and tumor necrosis factor-α(TNF-α). Taken together, based on the above research evidence, apoA-I and its peptide mimic may regulate the oxidative stress, TGF- β1/Smads signaling pathway and inflammatory response to reduce peritoneal fibrosis due to peritoneal dialysis.

Colchicine exerts anti-atherosclerotic and -plaque-stabilizing effects targeting foam cell formation

Colchicine is a broad-acting anti-inflammatory agent that has attracted interest for repurposing in atherosclerotic cardiovascular disease. Here, we studied its ability at a human equivalent dose of 0.5 mg/day to modify plaque formation and composition in murine atherosclerosis and investigated its actions on macrophage responses to atherogenic stimuli in vitro. In atherosclerosis induced by high-cholesterol diet, Apoe^-/- mice treated with colchicine had 50% reduction in aortic oil Red O⁺ plaque area compared to saline control (p = .001) and lower oil Red O⁺ staining of aortic sinus lesions (p = .03). In vitro, addition of 10 nM colchicine inhibited foam cell formation from murine and human macrophages after treatment with oxidized LDL (ox-LDL). Mechanistically, colchicine downregulated glycosylation and surface expression of the ox-LDL uptake receptor, CD36, and reduced CD36⁺ staining in aortic sinus plaques. It also decreased macrophage uptake of cholesterol crystals, resulting in lower intracellular lysosomal activity, inhibition of the NLRP3 inflammasome, and reduced secretion of IL-1β and IL-18. Colchicine's anti-atherosclerotic actions were accentuated in a mouse model of unstable plaque induced by carotid artery tandem stenosis surgery, where it decreased lesion size by 48% (p = .01), reduced lipid (p = .006) and necrotic core area (p = .007), increased collagen content and cap-to-necrotic core ratio (p = .05), and attenuated plaque neutrophil extracellular traps (p < .001). At low dose, colchicine's effects were not accompanied by the evidence of microtubule depolymerization. Together, these results show that colchicine exerts anti-atherosclerotic and plaque-stabilizing effects at low dose by inhibiting foam cell formation and cholesterol crystal-induced inflammation. This provides a new framework to support its repurposing for atherosclerotic cardiovascular disease.

Smoking status impacts treatment efficacy in smoke-induced lung inflammation: A pre-clinical study

Rationale: Smoking status and smoking history remain poorly accounted for as variables that could affect the efficacy of new drugs being tested in chronic obstructive pulmonary disease (COPD) patients. As a proof of concept, we used a pre-clinical model of cigarette smoke (CS) exposure to compare the impact of treatment during active CS exposure or during the cessation period on the anti-inflammatory effects IL-1α signaling blockade.

Methods: Mice were exposed to CS for 2 weeks, followed by a 1-week cessation, then acutely re-exposed for 2 days. Mice were treated with an anti-IL-1α antibody either during CS exposure or during cessation and inflammatory outcomes were assessed.

Results: We found that mice re-exposed to CS displayed reduced neutrophil counts and cytokine levels in the bronchoalveolar lavage (BAL) compared to mice exposed only acutely. Moreover, we found that treatment with an anti-IL-1α antibody during the initial CS exposure delayed inflammatory processes and interfered with pulmonary adaptation, leading to rebound pulmonary neutrophilia, increased BAL cytokine secretion (CCL2) and upregulated Mmp12 expression. Conversely, administration of anti-IL-1α during cessation had the opposite effect, improving BAL neutrophilia, decreasing CCL2 levels and reducing Mmp12 expression.

Discussion: These results suggest that pulmonary adaptation to CS exposure dampens inflammation and blocking IL-1α signaling during CS exposure delays the inflammatory response. More importantly, the same treatment administered during cessation hastens the return to pulmonary inflammatory homeostasis, strongly suggesting that smoking status and treatment timing should be considered when testing new biologics in COPD.

Endoplasmic Reticulum Stress and Pathogenesis of Vascular Calcification

Vascular calcification (VC) is characterized by calcium phosphate deposition in blood vessel walls and is associated with many diseases, as well as increased cardiovascular morbidity and mortality. However, the molecular mechanisms underlying of VC development and pathogenesis are not fully understood, thus impeding the design of molecular-targeted therapy for VC. Recently, several studies have shown that endoplasmic reticulum (ER) stress can exacerbate VC. The ER is an intracellular membranous organelle involved in the synthesis, folding, maturation, and post-translational modification of secretory and transmembrane proteins. ER stress (ERS) occurs when unfolded/misfolded proteins accumulate after a disturbance in the ER environment. Therefore, downregulation of pathological ERS may attenuate VC. This review summarizes the relationship between ERS and VC, focusing on how ERS regulates the development of VC by promoting osteogenic transformation, inflammation, autophagy, and apoptosis, with particular interest in the molecular mechanisms occurring in various vascular cells. We also discuss, the therapeutic effects of ERS inhibition on the progress of diseases associated with VC are detailed.

Post-Stroke Administration of L-4F Promotes Neurovascular and White Matter Remodeling in Type-2 Diabetic Stroke Mice

Patients with type 2 diabetes mellitus (T2DM) exhibit a distinct and high risk of ischemic stroke with worse post-stroke neurovascular and white matter (WM) prognosis than the non-diabetic population. In the central nervous system, the ATP-binding cassette transporter member A 1 (ABCA1), a reverse cholesterol transporter that efflux cellular cholesterol, plays an important role in high-density lipoprotein (HDL) biogenesis and in maintaining neurovascular stability and WM integrity. Our previous study shows that L-4F, an economical apolipoprotein A member I (ApoA-I) mimetic peptide, has neuroprotective effects via alleviating neurovascular and WM impairments in the brain of db/db-T2DM stroke mice. To further investigate whether L-4F has neurorestorative benefits in the ischemic brain after stroke in T2DM and elucidate the underlying molecular mechanisms, we subjected middle-aged, brain-ABCA1 deficient (ABCA1-B/-B), and ABCA1-floxed (ABCA1fl/fl) T2DM control mice to distal middle cerebral artery occlusion. L-4F (16 mg/kg, subcutaneous) treatment was initiated 24 h after stroke and administered once daily for 21 days. Treatment of T2DM-stroke with L-4F improved neurological functional outcome, and decreased hemorrhage, mortality, and BBB leakage identified by decreased albumin infiltration and increased tight-junction and astrocyte end-feet densities, increased cerebral arteriole diameter and smooth muscle cell number, and increased WM density and oligodendrogenesis in the ischemic brain in both ABCA1-B/-B and ABCA1fl/fl T2DM-stroke mice compared with vehicle-control mice, respectively (p < 0.05, n = 9 or 21/group). The L-4F treatment reduced macrophage infiltration and neuroinflammation identified by decreases in ED-1, monocyte chemoattractant protein-1 (MCP-1), and toll-like receptor 4 (TLR4) expression, and increases in anti-inflammatory factor Insulin-like growth factor 1 (IGF-1) and its receptor IGF-1 receptor β (IGF-1Rβ) in the ischemic brain (p < 0.05, n = 6/group). These results suggest that post-stroke administration of L-4F may provide a restorative strategy for T2DM-stroke by promoting neurovascular and WM remodeling. Reducing neuroinflammation in the injured brain may contribute at least partially to the restorative effects of L-4F independent of the ABCA1 signaling pathway.

Astragaloside IV protects against C/EBP homologous protein-mediated apoptosis in oxidized low-density lipoprotein-treated macrophages by promoting autophagy

Astragaloside Ⅳ (AS-Ⅳ) is one of the main active components extracted from Astragalus membranaceus that exerts an antiatherosclerotic effect. Our study explored the underlying anti-apoptotic effects and the mechanisms of action of AS-Ⅳ in oxidized low-density lipoprotein (oxLDL)-stimulated macrophages and in vulnerable plaques. The results showed that AS-Ⅳ lowered the oxLDL-induced lipid content and reversed the oxLDL-induced reduction in cell viability and elevation in lactate dehydrogenase (LDH) leakage and apoptosis in RAW264.7 macrophages, similar to the effects of 4-phenylbutyric acid (PBA, an ER stress inhibitor). In addition, consistent with the effect exerted by PBA, AS-Ⅳ inhibited oxLDL-triggered ER stress activation by decreasing the level of inositol-requiring enzyme1 phosphorylation and transcription factor 6 nuclear translocation and upregulating the protein and mRNA expression of glucose-regulated protein 78 (GPR78) and C/EBP homologous protein (CHOP). As expected, autophagy activation was induced by AS-IV, evidenced by increased expression of microtubule-associated protein 1 light chain 3-Ⅱ (LC3-Ⅱ), autophagy-related gene 5, and beclin-1 in macrophages. Furthermore, after pretreatment with 3-methyladenine and beclin-1 small interfering RNA, the inhibitory role played by AS-Ⅳ in oxLDL-induced ER stress-CHOP-mediated macrophage apoptosis was weakened, while its inhibitory effect was further enhanced by rapamycin pretreatment. Moreover, administration of AS-Ⅳ or rapamycin to Apoe^-/- mice upregulated LC3-Ⅱ expression and collagen content but decreased CHOP expression, macrophage apoptosis, and lipid areas. Overall, by promoting autophagy, AS-Ⅳ effectively protects macrophages from oxLDL-induced apoptosis mediated by ER stress-CHOP, which may reinforce the stability of atherosclerotic plaques.

D4F alleviates the C/EBP homologous protein-mediated apoptosis in glycated high-density lipoprotein-treated macrophages by facilitating autophagy

The present study aimed to investigate the role of D4F, an apolipoprotein A-I mimetic peptide, in macrophage apoptosis induced by the glycated high-density lipoprotein (gly-HDL)-induced endoplasmic reticulum (ER) stress C/EBP homologous protein (CHOP) pathway, and unravel the regulatory role of autophagy in this process. Our results revealed that except for suppressing the accumulation of lipids within RAW264.7 macrophages caused by gly-HDL, D4F inhibited gly-HDL-induced decrease in the cell viability and increase in lactate dehydrogenase leakage and cell apoptosis, which were similar to 4-phenylbutyric acid (PBA, an ER stress inhibitor). Besides, similar to PBA, D4F inhibited gly-HDL-induced ER stress response activation evaluated through the decreased PERK and eIF2α phosphorylation, together with reduced ATF6 nuclear translocation as well as the downregulation of GRP78 and CHOP. Interestingly, D4F facilitated gly-HDL-triggered activation of autophagy, measured as elevated levels of beclin-1, LC3-II, and ATG5 expressions in macrophages. Furthermore, the inhibition effect of D4F on gly-HDL-induced ER stress-CHOP-induced apoptosis of macrophages was restrained after beclin-1 siRNA and 3-methyladenine (3-MA, an inhibitor of autophagy) treatments, while this effect was further reinforced after rapamycin (Rapa, an inducer of autophagy) treatment. Furthermore, administering D4F or Rapa to T2DM mice upregulated LC3-II and attenuated CHOP expression, cell apoptosis, and atherosclerotic lesions. However, the opposite results were obtained when 3-MA was administered to these mice. These results support that D4F effectively protects macrophages against gly-HDL-induced ER stress-CHOP-mediated apoptosis by promoting autophagy.

Huotan Jiedu Tongluo Decoction Inhibits Balloon-Injury-Induced Carotid Artery Intimal Hyperplasia in the Rat through the PERK-eIF2α-ATF4 Pathway and Autophagy Mediation

In-stent restenosis (ISR) is the main factor affecting the outcome of percutaneous coronary intervention (PCI), and its main pathological feature is neointimal hyperplasia. Huotan Jiedu Tongluo decoction (HTJDTLD) is an effective traditional Chinese medicine (TCM) prescription for the treatment of vascular stenosis diseases. However, the precise anti-ISR mechanism of HTJDTLD remains unclear. Here, we investigated whether HTJDTLD can inhibit the excessive activation of endoplasmic reticulum stress (ERS) and reduce the level of autophagy factors through regulating the PERK-eIF2α-ATF4 pathway, thereby inhibiting the proliferation of the intima of blood vessels damaged by balloon injury (BI) and preventing the occurrence of ISR. In this study, a 2F Fogarty balloon was used to establish a common carotid artery (CCA) BI model in male Sprague-Dawley rats. Then, HTJDTLD (16.33 g/kg/d) or atorvastatin (1.19 mg/kg/d) was administered by gavage. Four weeks later, hematoxylin-eosin (HE) and Masson staining of the injured CCA were performed to observe the histological changes in the CCA. Immunohistochemistry (IHC) was used to assess the proliferation and dedifferentiation of vascular smooth muscle cells (VSMCs) in the CCA. Western blotting and RT-PCR were used to measure the expression of ERS- and autophagy-related proteins and mRNAs in the CCA. The results indicated that HTJDTLD significantly alleviated BI-induced carotid artery intimal hyperplasia and fibrosis and reduced the neointimal area (NIA) and NIA/medial area (MA) ratio. In addition, HTJDTLD inhibited the proliferation and dedifferentiation of VSMCs, reduced the expression of proliferating cell nuclear antigen (PCNA), and increased the smooth-muscle-α-actin- (SMα-actin-) positive area. HTJDTLD also significantly reduced the expression of the ERS-related factors: GRP78, p-PERK/PERK, p-eIF2α/eIF2α, ATF4, and CHOP. In addition, the expression of the autophagy-related factors, Beclin1, LC3B, and ATG12, was significantly decreased. In addition, in vitro experiments showed that HTJDTLD inhibited the above-mentioned ERS signal molecules in human umbilical vein endothelial cells (HUVEC) and rat aortic smooth muscle cells (A7R5) induced by tunicamycin (TM) and played a crucial role in protecting cells from damage. HTJDTLD may be a very promising drug for the treatment of ISR.

Apolipoprotein-AI and AIBP synergetic anti-inflammation as vascular diseases therapy: the new perspective

Vascular diseases (VDs) including pulmonary arterial hypertension (PAH), atherosclerosis (AS) and coronary arterial diseases (CADs) contribute to the higher morbidity and mortality worldwide. Apolipoprotein A-I (Apo A-I) binding protein (AIBP) and Apo-AI negatively correlate with VDs. However, the mechanism by which AIBP and apo-AI regulate VDs still remains unexplained. Here, we provide an overview of the role of AIBP and apo-AI regulation of vascular diseases molecular mechanisms such as vascular energy homeostasis imbalance, oxidative and endoplasmic reticulum stress and inflammation in VDs. In addition, the role of AIBP and apo-AI in endothelial cells (ECs), vascular smooth muscle (VSMCs) and immune cells activation in the pathogenesis of VDs are explained. The in-depth understanding of AIBP and apo-AI function in the vascular system may lead to the discovery of VDs therapy.

D4F prophylaxis enables redox and energy homeostasis while preventing inflammation during hypoxia exposure

Apo-A1 is correlated with conditions like hyperlipidemia, cardiovascular diseases, high altitude pulmonary edema and etc. where hypoxia constitutes an important facet.Hypoxia causes oxidative stress, vaso-destructive and inflammatory outcomes.Apo-A1 is reported to have vasoprotective, anti-oxidative, anti-apoptotic, and anti-inflammatory effects. However, effects of Apo-A1 augmentation during hypoxia exposure are unknown.In this study, we investigated the effects of exogenously supplementing Apo-A1-mimetic peptide on SD rats during hypoxia exposure. For easing the processes of delivery, absorption and bio-availability, Apo-A1 mimetic peptide D4F was used. The rats were given 10 mg/kg BW dose (i.p.) of D4F for 7 days and then exposed to hypoxia. D4F was observed to attenuate both oxidative stress and inflammation during hypoxic exposure. D4F improved energy homeostasis during hypoxic exposure. D4F did not affect HIF-1a levels during hypoxia but increased MnSOD levels while decreasing CRP and Apo-B levels. D4F showed promise as a prophylactic against hypoxia exposure.

Study on the protective effect and mechanism of Dicliptera chinensis (L.) Juss (Acanthaceae) polysaccharide on immune liver injury induced by LPS

The purpose of this study is to use Dicliptera chinensis (L.) Juss (Acanthaceae) polysaccharide (DCP) to act on the NF-κB inflammatory pathway and Fas/FasL ligand system, in order to find a new method to improve immune liver injury. Lipopolysaccharide (LPS) was used to establish an injury model in vivo (Kunming mice) and in vitro (LO2 cells). In this experiment, hematoxylin-eosin (H&E) staining and related biochemical indicators were used to observe the pathological changes of liver tissues, oxidative stress and inflammatory reactions. Immunohistochemistry, ELISA, RT-PCR and Western blot were used to detect protein or mRNA expressions associated with inflammation response and apoptosis. The experimental results show that the model group has obvious liver cell damage and inflammatory infiltration. After DCP intervention, it could significantly reduce the levels of ALT, AST, ALP, TBIL and MDA in serum, and increase the content of SOD and GSH-Px. In addition, DCP can reduce the expression level of NF-κB in the liver and reduce the release of downstream inflammatory factors TNF-α, IL-6 and IL-1β, thereby reducing the inflammation. At the same time, DCP can significantly inhibit the expression of Fas/FasL ligand system and apoptosis related-proteins and mRNA, which in turn can reduce cell apoptosis. In conclusion, DCP can alleviate liver injury by inhibiting liver inflammation and apoptosis, which provides a new strategy for clinical treatment of immune liver injury.

The role of CD36 in cardiovascular disease

CD36, also known as the scavenger receptor B2, is a multifunctional receptor widely expressed in various organs. CD36 plays a crucial role in the uptake of long-chain fatty acids, the main metabolic substrate in myocardial tissue. The maturation and transportation of CD36 is regulated by post-translational modifications, including phosphorylation, ubiquitination, glycosylation, and palmitoylation. CD36 is decreased in pathological cardiac hypertrophy caused by ischaemia-reperfusion and pressure overload, and increased in diabetic cardiomyopathy and atherosclerosis. Deficiency of CD36 alleviates diabetic cardiomyopathy and atherosclerosis, while overexpression of CD36 eliminates ischaemia-reperfusion damage, together suggesting that CD36 is closely associated with the progression of cardiovascular diseases and may be a new therapeutic target. This review summarizes the regulation and post-translational modifications of CD36 and evaluates its role in cardiovascular diseases and its potential as a therapeutic target.

Role of the Scavenger Receptor CD36 in Accelerated Diabetic Atherosclerosis

Diabetes mellitus entails increased atherosclerotic burden and medial arterial calcification, but the precise mechanisms are not fully elucidated. We aimed to investigate the implication of CD36 in inflammation and calcification processes orchestrated by vascular smooth muscle cells (VSMCs) under hyperglycemic and atherogenic conditions. We examined the expression of CD36, pro-inflammatory cytokines, endoplasmic reticulum (ER) stress markers, and mineralization-regulating enzymes by RT-PCR in human VSMCs, cultured in a medium containing normal (5 mM) or high glucose (22 mM) for 72 h with or without oxidized low-density lipoprotein (oxLDL) (24 h). The uptake of 1,1′-dioctadecyl-3,3,3′,3-tetramethylindocarbocyanine perchlorate-fluorescently (DiI) labeled oxLDL was quantified by flow cytometry and fluorimetry and calcification assays were performed in VSMC cultured in osteogenic medium and stained by alizarin red. We observed induction in the expression of CD36, cytokines, calcification markers, and ER stress markers under high glucose that was exacerbated by oxLDL. These results were confirmed in carotid plaques from subjects with diabetes versus non-diabetic subjects. Accordingly, the uptake of DiI-labeled oxLDL was increased after exposure to high glucose. The silencing of CD36 reduced the induction of CD36 and the expression of calcification enzymes and mineralization of VSMC. Our results indicate that CD36 signaling is partially involved in hyperglycemia and oxLDL-induced vascular calcification in diabetes.

Amorphous silica nanoparticles accelerated atherosclerotic lesion progression in ApoE-/- mice through endoplasmic reticulum stress-mediated CD36 up-regulation in macrophage

Background

The biosafety concern of silica nanoparticles (SiNPs) is rapidly expanding alongside with its mass production and extensive applications. The cardiovascular effects of SiNPs exposure have been gradually confirmed, however, the interaction between SiNPs exposure and atherosclerosis, and the underlying mechanisms still remain unknown. Thereby, this study aimed to explore the effects of SiNPs on the progression of atherosclerosis, and to investigate related mechanisms.

Results

We firstly investigated the in vivo effects of SiNPs exposure on atherosclerosis via intratracheal instillation of ApoE^−/− mice fed a Western diet. Ultrasound microscopy showed a significant increase of pulse wave velocity (PWV) compared to the control group, and the histopathological investigation reflected a greater plaque burden in the aortic root of SiNPs-exposed ApoE^−/− mice. Compared to the control group, the serum levels of total triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C) were elevated after SiNPs exposure. Moreover, intensified macrophage infiltration and endoplasmic reticulum (ER) stress was occurred in plaques after SiNPs exposure, as evidenced by the upregulated CD68 and CHOP expressions. Further in vitro, SiNPs was confirmed to activate ER stress and induce lipid accumulation in mouse macrophage, RAW264.7. Mechanistic analyses showed that 4-PBA (a classic ER stress inhibitor) pretreatment greatly alleviated SiNPs-induced macrophage lipid accumulation, and reversed the elevated CD36 expression induced by SiNPs.

Conclusions

Our results firstly revealed the acceleratory effect of SiNPs on the progression of atherosclerosis in ApoE^−/− mice, which was related to lipid accumulation caused by ER stress-mediated upregulation of CD36 expression in macrophage.

Graphical abstract

Endoplasmic Reticulum Stress in Macrophages: The Vicious Circle of Lipid Accumulation and Pro-Inflammatory Response

The endoplasmic reticulum (ER) stress is an important event in the pathogenesis of different human disorders, including atherosclerosis. ER stress leads to disturbance of cellular homeostasis, apoptosis, and in the case of macrophages, to foam cell formation and pro-inflammatory cytokines production. In atherosclerosis, several cell types can be affected by ER stress, including endothelial cells, vascular smooth muscular cells, and macrophages. Modified low-density lipoproteins (LDL) and cytokines, in turn, can provoke ER stress through different processes. The signaling cascades involved in ER stress initiation are complex and linked to other cellular processes, such as lysosomal biogenesis and functioning, autophagy, mitochondrial homeostasis, and energy production. In this review, we discuss the underlying mechanisms of ER stress formation and the interplay of lipid accumulation and pro-inflammatory response. We will specifically focus on macrophages, which are the key players in maintaining chronic inflammatory milieu in atherosclerotic lesions, and also a major source of lipid-accumulating foam cells.

Thioredoxin-1 blocks methamphetamine-induced injury in brain through inhibiting endoplasmic reticulum and mitochondria-mediated apoptosis in mice

Methamphetamine (METH) has been reported to induce endoplasmic reticulum (ER) stress and neuronal apoptosis in the central nervous system (CNS) during the development of addiction. Thioredoxin-1 (Trx-1) is a redox regulating protein and plays an important role in inhibiting apoptosis and protects neurons from cytotoxicity through ER and mitochondria-mediated pathways. Our previous study has been reported that Trx-1 protects mice from METH-induced rewarding effect. However, whether Trx-1 plays the role in resisting METH injury is still unclear. Here, we aim to investigate whether Trx-1 participates in the regulation of METH-induced CNS injury via ER stress and mitochondria-mediated pathways. Our study first repeated the conditioned place preference expression induced by METH. Then we detected and found that METH increased the expression of N-methyl-d-asparate (NMDA) receptor subunit 2B (NR2B) and the level of glutamate (Glu) in the ventral tegmental area (VTA) and nucleus accumbens (NAc), while Trx-1 overexpression suppressed the increases. We further examined ER stress-related proteins and mitochondrial apoptosis pathway in the VTA and NAc, and found that METH increased the expressions of glucose regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), and Bax, as same time decreased the expressions of procaspase12, Bcl-2, and procaspase3, while Trx-1 overexpression blocked these changes. These results indicate that Trx-1 blocks METH-induced injury by suppressing ER stress and mitochondria-mediated apoptosis in the VTA and NAc via targeting glutamatergic system.

Ox-LDL Causes Endothelial Cell Injury Through ASK1/NLRP3-Mediated Inflammasome Activation via Endoplasmic Reticulum Stress

Objective

This study was to investigate the mechanism of inflammatory pathology modification induced by ox-LDL in endothelial cells.

Methodology

In this study, we firstly investigated the efflux of cholesterol of endothelial cells under the treatment of ox-LDL, and cell proliferation, ROS production, cell apoptosis was measured. Further, proteins of ASK1, NLRP3 inflammasomes and endoplasmic reticulum stress response were detected. Afterwards, ASK1 inhibitor (GS-4997) or endoplasmic reticulum stress (ERS) inhibitor (4-PBA) was used to measure the performance of endothelial cells.

Results

In this study, endothelial cells were treated with ox-LDLs alone or in combination with a GS-4997 or 4-PBA. Results showed that ox-LDLs attenuated the efflux of cholesterol from endothelial cells in a dose-dependent manner. Ox-LDLs inhibited the proliferation of endothelial cells, and induced their apoptosis and production of reactive oxygen species (ROS). Additionally, ox-LDLs upregulated the levels of phosphorylated ASK1, ERS-related proteins (chop, p-PERK, GRP78, and p-IRE-1), and inflammation-associated proteins (NLRP3, IL-1β, and caspase 1) in endothelial cells. Moreover, we proved that GS-4997 could partly reverse ox-LDL-mediated cell proliferation, apoptosis, ROS production, and inflammation in endothelial cells, and increase cholesterol efflux. We also found that 4-PBA could attenuate the effects of ox-LDLs on endothelial cell cholesterol efflux, proliferation, apoptosis, ROS production, and inflammation.

Conclusion

Our results suggest that cholesterol efflux from endothelial cells is reduced by ox-LDLs, and these reductions in cholesterol efflux are accompanied by increased NLRP3 inflammasome signaling, ASK1 and higher levels of endoplasmic reticulum stress. Our results suggest this axis as potential targets for treating atherosclerosis.

Role of pyruvate kinase M2 in oxidized LDL-induced macrophage foam cell formation and inflammation

Pyruvate kinase M2 (PKM2) links metabolic and inflammatory dysfunction in atherosclerotic coronary artery disease; however, its role in oxidized LDL (Ox-LDL)-induced macrophage foam cell formation and inflammation is unknown and therefore was studied. In recombinant mouse granulocyte-macrophage colony-stimulating factor-differentiated murine bone marrow-derived macrophages, early (1-6 h) Ox-LDL treatment induced PKM2 tyrosine 105 phosphorylation and promotes its nuclear localization. PKM2 regulates aerobic glycolysis and inflammation because PKM2 shRNA or Shikonin abrogated Ox-LDL-induced hypoxia-inducible factor-1α target genes lactate dehydrogenase, glucose transporter member 1, interleukin 1β (IL-1β) mRNA expression, lactate, and secretory IL-1β production. PKM2 inhibition significantly increased Ox-LDL-induced ABCA1 and ABCG1 protein expression and NBD-cholesterol efflux to apoA1 and HDL. PKM2 shRNA significantly inhibited Ox-LDL-induced CD36, FASN protein expression, DiI-Ox-LDL binding and uptake, and cellular total cholesterol, free cholesterol, and cholesteryl ester content. Therefore, PKM2 regulates lipid uptake and efflux. DASA-58, a PKM2 activator, downregulated LXR-α, ABCA1, and ABCG1, and augmented FASN and CD36 protein expression. Peritoneal macrophages showed similar results. Ox-LDL induced PKM2- SREBP-1 interaction and FASN expression in a PKM2-dependent manner. Therefore, this study suggests a role for PKM2 in Ox-LDL-induced aerobic glycolysis, inflammation, and macrophage foam cell formation.

Tanshinone IIA ameliorates cognitive deficits by inhibiting endoplasmic reticulum stress-induced apoptosis in APP/PS1 transgenic mice

Our previous data indicated that tanshinone IIA (tan IIA) improves learning and memory in a mouse model of Alzheimer's disease (AD) induced by streptozotocin via restoring cholinergic function, attenuating oxidative stress and blocking p38 MAPK signal pathway activation. This study aims to estimate whether tan IIA inhibits endoplasmic reticulum (ER) stress-induced apoptosis to prevent cognitive decline in APP/PS1 transgenic mice. Tan IIA (10 mg/kg and 30 mg/kg) was intraperitoneally administered to the six-month-old APP/PS1 mice for 30 consecutive days. β-amyloid (Aβ) plaques were measured by immunohistochemisty and Thioflavin S staining, apoptotic cells were observed by TUNEL, ER stress markers and apoptosis signaling proteins were investigated by western blotting and RT-PCR. Our results showed that tan IIA significantly ameliorates cognitive deficits and improves spatial learning ability of APP/PS1 mice in the nest-building test, novel object recognition test and Morris water maze test. Furthermore, tan IIA significantly reduced the deposition of Aβ plaques and neuronal apoptosis, and markedly prevented abnormal expression of glucose regulated protein 78 (GRP78), initiation factor 2α (eIF2α), inositol-requiring enzyme 1α (IRE1α), activating transcription factor 6 (ATF6), as well as suppressed the activation of C/EBP homologous protein (CHOP) and c-Jun N-terminal kinase (JNK) pathways in the parietal cortex and hippocampus. Moreover, tan IIA induced an up-regulation of the Bcl-2/Bax ratio and down-regulation of caspase-3 protein activity. Taken together, the above findings indicated that tan IIA improves learning and memory through attenuating Aβ plaques deposition and inhibiting ER stress-induced apoptosis. These results suggested that tan IIA might become a promising therapeutic candidate drug against AD.

ApoA-I Mimetic Peptide Reduces Vascular and White Matter Damage After Stroke in Type-2 Diabetic Mice

Diabetes leads to an elevated risk of stroke and worse functional outcome compared to the general population. We investigate whether L-4F, an economical ApoA-I mimetic peptide, reduces neurovascular and white-matter damage in db/db type-2 diabetic (T2DM) stroke mice. L-4F (16 mg/kg, subcutaneously administered initially 2 h after stroke and subsequently daily for 4 days) reduced hemorrhagic transformation, decreased infarct-volume and mortality, and treated mice exhibited increased cerebral arteriole diameter and smooth muscle cell number, decreased blood-brain barrier leakage and white-matter damage in the ischemic brain as well as improved neurological functional outcome after stroke compared with vehicle-control T2DM mice (p < 0.05, n = 11/group). Moreover, administration of L-4F mitigated macrophage infiltration, and reduced the level of proinflammatory mediators tumor necrosis factor alpha (TNFα), high-mobility group box-1 (HMGB-1)/advanced glycation end-product receptor (RAGE) and plasminogen activator inhibitor-1 (PAI-1) in the ischemic brain in T2DM mice (p < 0.05, n = 6/group). In vitro, L-4F treatment did not increase capillary-like tube formation in mouse-brain endothelial cells, but increased primary artery explant cell migration derived from C57BL/6-aorta 1 day after middle cerebral artery occlusion (MCAo), and enhanced neurite-outgrowth after 2 h of oxygen-glucose deprivation and axonal-outgrowth in primary cortical neurons derived from the C57BL/6-embryos subjected to high-glucose condition. This study suggests that early treatment with L-4F provides a potential strategy to reduce neuroinflammation and vascular and white-matter damage in the T2DM stroke population.

Lipid-regulating properties of butyric acid and 4-phenylbutyric acid: Molecular mechanisms and therapeutic applications

In the past two decades, significant advances have been made in the etiology of lipid disorders. Concomitantly, the discovery of liporegulatory functions of certain short-chain fatty acids has generated interest in their clinical applications. In particular, butyric acid (BA) and its derivative, 4-phenylbutyric acid (PBA), which afford health benefits against lipid disorders while being generally well tolerated by animals and humans have been assessed clinically. This review examines the evidence from cell, animal and human studies pertaining to the lipid-regulating effects of BA and PBA, their molecular mechanisms and therapeutic potential. Collectively, the evidence supports the view that intakes of BA and PBA benefit lipid homeostasis across biological systems. We reviewed the evidence that BA and PBA downregulate de novo lipogenesis, ameliorate lipotoxicity, slow down atherosclerosis progression, and stimulate fatty acid β-oxidation. Central to their mode of action, BA appears to function as a histone deacetylase (HDAC) inhibitor while PBA acts as a chemical chaperone and/or a HDAC inhibitor. Areas of further inquiry include the effects of BA and PBA on adipogenesis, lipolysis and apolipoprotein metabolism.

Pharmacological activation of liver X receptor during cigarette smoke exposure adversely affects alveolar macrophages and pulmonary surfactant homeostasis

Smoking alters pulmonary reverse lipid transport and leads to intracellular lipid accumulation in alveolar macrophages. We investigated whether stimulating reverse lipid transport with an agonist of the liver X receptor (LXR) would help alveolar macrophages limit lipid accumulation and dampen lung inflammation in response to cigarette smoke. Mice were exposed to cigarette smoke and treated intraperitoneally with the LXR agonist T0901317. Expression of lipid capture and lipid export genes was assessed in lung tissue and alveolar macrophages. Pulmonary inflammation was assessed in the bronchoalveolar lavage (BAL). Finally, cholesterol efflux capacity and pulmonary surfactant levels were determined. In room air-exposed mice, T0901317 increased the expression of lipid export genes in macrophages and the whole lung and increased cholesterol efflux capacity without inducing inflammation or affecting the pulmonary surfactant. However, cigarette smoke-exposed mice treated with T0901317 showed a marked increase in BAL neutrophils, IL-1α, C-C motif chemokine ligand 2, and granulocyte-colony-stimulating factor levels. T0901317 treatment in cigarette smoke-exposed mice failed to increase the ability of alveolar macrophages to export cholesterol and markedly exacerbated IL-1α release. Finally, T0901317 led to pulmonary surfactant depletion only in cigarette smoke-exposed mice. This study shows that hyperactivation of LXR and the associated lipid capture/export mechanisms only have minor pulmonary effects on the normal lung. However, in the context of cigarette smoke exposure, where the pulmonary surfactant is constantly oxidized, hyperactivation of LXR has dramatic adverse effects, once again showing the central role of lipid homeostasis in the pulmonary response to cigarette smoke exposure.

Endoplasmic reticulum stress-dependent autophagy inhibits glycated high-density lipoprotein-induced macrophage apoptosis by inhibiting CHOP pathway

This study was designed to explore the inductive effect of glycated high‐density lipoprotein (gly‐HDL) on endoplasmic reticulum (ER) stress‐C/EBP homologous protein (CHOP)‐mediated macrophage apoptosis and its relationship with autophagy. Our results showed that gly‐HDL caused macrophage apoptosis with concomitant activation of ER stress pathway, including nuclear translocation of activating transcription factor 6, phosphorylation of protein kinase‐like ER kinase (PERK) and eukaryotic translation initiation factor 2α, and CHOP up‐regulation, which were inhibited by 4‐phenylbutyric acid (PBA, an ER stress inhibitor) and the gene silencing of PERK and CHOP. Similar data were obtained from macrophages treated by HDL isolated from diabetic patients. Gly‐HDL induced macrophage autophagy as assessed by up‐regulation of beclin‐1, autophagy‐related gene 5 and microtubule‐associated protein one light chain 3‐II, which were depressed by PBA and PERK siRNA. Gly‐HDL‐induced apoptosis, PERK phosphorylation and CHOP up‐regulation were suppressed by rapamycin (an autophagy inducer), whereas aggravated by 3‐methyladenine (an autophagy inhibitor) and beclin‐1 siRNA. Administration of diabetic apoE^−/− mice with rapamycin attenuated MOMA‐2 and CHOP up‐regulation and apoptosis in atherosclerotic lesions. These data indicate that gly‐HDL may induce macrophage apoptosis through activating ER stress‐CHOP pathway and ER stress mediates gly‐HDL‐induced autophagy, which in turn protects macrophages against apoptosis by alleviating CHOP pathway.

Protective effects of tanshinone IIA on SH-SY5Y cells against oAβ1-42-induced apoptosis due to prevention of endoplasmic reticulum stress

Endoplasmic reticulum (ER) stress caused by β-amyloid protein (Aβ) may play an important role in the pathogenesis of Alzheimer disease (AD). Our previous data have indicated that tanshinone IIA (tan IIA) protected primary neurons from Aβ induced neurotoxicity. To further explore the neuroprotection of tan IIA, here we study the effects of tan IIA on the ER stress response in oligomeric Aβ_1-42 (oAβ_1-42)-induced SH-SY5Y cell injury. Our data showed that tan IIA pretreatment could increase cell viability and inhibit apoptosis caused by oAβ_1-42. Furthermore, tan IIA markedly suppressed ER dilation and prevented oAβ_1-42-induced abnormal expression of glucose regulated protein 78 (GRP78), initiation factor 2α (eIF2α), activating transcription factor 6 (ATF6), as well as inhibited the activation of C/EBP homologous protein (CHOP) and c-Jun N-terminal kinase (JNK) pathways. Moreover, tan IIA ameliorated oAβ_1-42-induced Bcl-2/Bax ratio reduction, prevented cytochrome c translocation into cytosol from mitochondria, reduced oAβ_1-42-induced cleavage of caspase-9 and caspase-3, suppressed caspase-3/7 activity, and increased mitochondrial membrane potential (MMP) and ATP content. Meanwhile, oAβ_1-42-induced cell apoptosis and activation of ER stress can also be attenuated by the inhibitor of ER stress 4-phenylbutyric acid (4-PBA). Taken together, these data indicated that tan IIA protects SH-SY5Y cells against oAβ_1-42-induced apoptosis through attenuating ER stress, modulating CHOP and JNK pathways, decreasing the expression of cytochrome c, cleaved caspase-9 and cleaved caspase-3, as well as increasing the ratio of Bcl-2/Bax, MMP and ATP content. Our results strongly suggested that tan IIA may be effective in treating AD associated with ER stress.

Estrogen and propofol combination therapy inhibits endoplasmic reticulum stress and remarkably attenuates cerebral ischemia-reperfusion injury and OGD injury in hippocampus

AIM

Endoplasmic reticulum stress (ERS) is vital in inducing apoptosis via caspase-12 and C/EBP homologous protein (CHOP) apoptotic pathway in the hippocampus after ischemia-reperfusion injury. The study aimed to estimate the efficacy of estrogen and propofol combination therapy against ERS-induced apoptosis after cerebral ischemia-reperfusion injury and oxygen-glucose deprivation (OGD) injury in the hippocampus in vivo and in vitro.

METHODS

Rat model of cerebral ischemia-reperfusion injury was generated by middle cerebral artery occlusion (MCAO) strategy with ischemic intervention for 90 min and reperfusion for 24 h. Propofol processing ischemia-reperfusion group (Propofol group) infused 50 mg/kg/h of propofol via the femoral vein at the onset of reperfusion for 30 min. Estrogen processing ischemia-reperfusion group (estrogen group) received 0.0125 mg/kg of estrogen via tail vein at 30 min prior to MCAO. Combination therapy for ischemia-reperfusion group (combination group) received simultaneous processing with propofol and estrogen. In vitro, brain slices were randomly exposed to dimethylsulfoxide (DSMO), 10 μm of propofol, 10 nm of estrogen, or propofol and estrogen. Changes in the orthodromic population spike (OPS) at the end of reoxygenation were recorded. Neurological deficit examination, Nissl staining, and 2,3,5-triphenyltetrazolium chloride (TTC) staining were employed to evaluate the level of cerebral ischemia-reperfusion injury. The expression of caspase-3, caspase-12, glucose-regulated protein 78 (GRP78), and CHOP were investigated by Western blot and immunofluorescence staining assays. Neural apoptotic rate in hippocampus was detected by the flow cytometry trial.

RESULTS

Neurological deficit score, infarct volume, the expression of caspase-3 (P <  0.05), caspase-12, GRP78, CHOP, and neural apoptotic rate of I/R group increased markedly (P <  0.01). When obtaining drug treatment, neurological deficit score (P <  0.05), infarct volume, the expression levels of caspase-12 and GRP78, and neural apoptotic rate of the propofol group decreased significantly (P <  0.01). Furthermore, neurological deficit score, infarct volume, expression levels of caspase-3, caspase-12, GRP78, and CHOP (P <  0.05), and neural apoptotic rate decreased in the estrogen group (P <  0.01) and especially in the combination group (P <  0.01). Compared with the propofol group, the neurological deficit score (P <  0.05), infarct volume, caspase-3, caspase-12, GRP78, CHOP, and neural apoptotic rate of the combination group decreased (P <  0.01). Compared with the estrogen group, the infarct volume, caspase-3 (P <  0.05), GRP78, CHOP, and neural apoptotic rate (P <  0.05) of the combination group decreased (P <  0.01). Compared with the propofol group, the infarct volume, caspase-3, caspase-12 (P <  0.05), and GRP78 (P <  0.05) of the estrogen group decreased (P <  0.01). Propofol and estrogen treatment can delay the abolishing time of OPS and increase the recovery rate and amplitude of OPS, compared with OGD group (P <  0.01), especially in the combination therapy (P <  0.01).

CONCLUSION

The neuroprotection of propofol and estrogen combination therapy inhibited excessive ERS-induced apoptosis against cerebral ischemia-reperfusion injury and OGD injury in the hippocampus of rats. Furthermore, the outcomes demonstrated that combination therapy yielded synergistic effects.

Silica nanoparticles promote oxLDL-induced macrophage lipid accumulation and apoptosis via endoplasmic reticulum stress signaling

Oxidized low-density lipoprotein (oxLDL), a marker of hyperlipidemia, plays a pivotal role in the development of atherosclerosis through the induction of macrophage-derived foam cell formation and thereafter apoptosis. Previous studies have indicated that silica nanoparticle (SiNPs) may exert a proatherogenic role, which could induce endothelial dysfunction, and monocytes infiltration. However, little is known about SiNPs' effects on macrophage-derived foam cell formation and apoptosis in the pathogenesis of atherosclerosis. In this study, we investigated the effects of SiNPs and oxLDL coexposure on macrophage-derived lipid metabolism, foam cell and apoptosis by using Raw264.7 cells. As a result, SiNPs enhanced cytotoxicity, apoptosis, and lipid accumulation upon oxLDL stimulation. Furthermore, quantitative determination of the expression levels of genes involved in cholesterol influx or efflux showed significantly up-regulated expressions of CD36 and SRA, whereas down-regulated expressions of ATP-binding cassette A1 (ABCA1), ABCG1, and SRB1 in oxLDL-treated macrophages, especially upon the co-exposure with SiNPs. It indicated that SiNPs promoted lipid accumulation in macrophage cells through not only facilitating cholesterol influx but also inhibiting cholesterol efflux. Endoplasmic reticulum (ER) is specialized for the production, modification, even trafficking of lipids. Interestingly, ER response was triggered upon oxLDL treatment, while SiNPs coexposure augmented the ER stress. Taken together, our results revealed that SiNPs promoted oxLDL-induced macrophage foam cell formation and apoptosis, which may be mediated by ER stress signaling. Thus we propose future researches needed for a better understanding of NPs' toxicity and their interactions with various pathophysiological conditions.

l-Glutamine Attenuates Apoptosis Induced by Endoplasmic Reticulum Stress by Activating the IRE1α-XBP1 Axis in IPEC-J2: A Novel Mechanism of l-Glutamine in Promoting Intestinal Health

Intestinal absorption and barrier malfunctions are associated with endoplasmic reticulum stress (ERS) in the intestine. We induced ERS by exposing the intestinal porcine epithelial cell line J2 (IPEC-J2) to tunicamycin (TUNI) to explore the potential of l-glutamine to reduce ERS-induced apoptosis. Our experiments demonstrated that exposing cells to TUNI results in spontaneous ERS and encourages the upregulation of glucose-regulated protein 78 (GRP78). Prolonged TUNI-induced ERS was found to increase apoptosis mediated by C/enhancer binding protein homologous protein (CHOP), accompanied by GRP78 downregulation. Treatment with l-glutamine was found to promote cell proliferation within the growth medium but to have little effect in basic Dulbecco’s modified Eagle medium. Finally, in the milieu of TUNI-induced ERS, l-glutamine was found to maintain a high level of GRP78, alleviate CHOP-mediated apoptosis and activate the inositol requiring enzyme 1α (IRE1α)-X-box binding protein 1 (XBP1) axis. A specific inhibitor of the IRE1α-XBP1 axis reversed the protective effect of l-glutamine by blocking the expression of IRE1α/XBP1s. We propose that the functional effect of l-glutamine on intestinal health may be partly due to its modulation of ERS and CHOP-mediated apoptosis.

D4F alleviates macrophage-derived foam cell apoptosis by inhibiting the NF-κB-dependent Fas/FasL pathway

This study was designed to explore the protective effect of D4F, an apolipoprotein A-I mimetic peptide, on nuclear factor-κB (NF-κB)-dependent Fas/Fas ligand (FasL) pathway-mediated apoptosis in macrophages induced by oxidized low-density lipoprotein (ox-LDL). Our results showed that ox-LDL induced apoptosis, NF-κB P65 nuclear translocation and the upregulation of Fas/FasL pathway-related proteins, including Fas, FasL, Fas-associated death domain proteins (FADD), caspase-8 and caspase-3 in RAW264.7 macrophages, whereas silencing of Fas blocked ox-LDL-induced macrophage apoptosis. Furthermore, silencing of P65 attenuated macrophage apoptosis and the upregulation of Fas caused by ox-LDL, whereas P65 expression was not significantly affected by treatment with Fas siRNA. D4F attenuated the reduction of cell viability and the increase in lactate dehydrogenase leakage and apoptosis. Additionally, D4F inhibited ox-LDL-induced P65 nuclear translocation and upregulation of Fas/FasL pathway-related proteins in RAW264.7 cells and in atherosclerotic lesions of apoE^-/- mice. However, Jo2, a Fas-activating monoclonal antibody, reversed the inhibitory effect of D4F on ox-LDL-induced cell apoptosis and upregulation of Fas, FasL and FADD. These data indicate that NF-κB mediates Fas/FasL pathway activation and apoptosis in macrophages induced by ox-LDL and that D4F protects macrophages from ox-LDL-induced apoptosis by suppressing the activation of NF-κB and the Fas/FasL pathway.

Overexpression of apolipoprotein A-I alleviates endoplasmic reticulum stress in hepatocytes

Background

Abnormal lipid metabolism may contribute to an increase in endoplasmic reticulum (ER) stress, resulting in the pathogenesis of non-alcoholic steatohepatitis. Apolipoprotein A-I (apoA-I) accepts cellular free cholesterol and phospholipids transported by ATP-binding cassette transporter A1 to generate nascent high density lipoprotein particles. Previous studies have revealed that the overexpression of apoA-I alleviated hepatic lipid levels by modifying lipid transport. Here, we examined the effects of apoA-I overexpression on ER stress and genes involved in lipogenesis in both HepG2 cells and mouse hepatocytes.

Methods

Human apoA-I was overexpressed in HepG2 hepatocytes, which were then treated with 2 μg/mL tunicamycin or 500 μM palmitic acid. Eight-week-old male apoA-I transgenic or C57BL/6 wild-type mice were intraperitoneally injected with 1 mg/kg body weight tunicamycin or with saline. At 48 h after injecting, blood and liver samples were collected.

Results

The overexpression of apoA-I in the models above resulted in decreased protein levels of ER stress makers and lipogenic gene products, including sterol regulatory element binding protein 1, fatty acid synthase, and acetyl-CoA carboxylase 1. In addition, the cellular levels of triglycerides and free cholesterol also decreased. Some of gene products which are related to ER stress-associated apoptosis were also affected by apoA-I overexpression. These results suggested that apoA-I overexpression could reduce steatosis by decreasing lipid levels and by suppressing ER stress and lipogenesis in hepatocytes.

Conclusion

ApoA-I expression could significantly reduce hepatic ER stress and lipogenesis in hepatocytes.

The apolipoprotein A-I mimetic peptide, D-4F, alleviates ox-LDL-induced oxidative stress and promotes endothelial repair through the eNOS/HO-1 pathway

Apolipoprotein A-I (apoA-I) mimetic peptide exerts many anti-atherogenic properties. However, the underlying mechanisms related to the endothelial protective effects remain elusive. In this study, the apoA-I mimetic peptide, D-4F, was used. Proliferation assay, wound healing, and transwell migration experiments showed that D-4F improved the impaired endothelial proliferation and migration resulting from ox-LDL. Endothelial adhesion molecules expression and monocyte adhesion assay demonstrated that D-4F inhibited endothelial inflammation. Caspase-3 activation and TUNEL stain indicated that D-4F reduced endothelial cell apoptosis. A pivotal anti-oxidant enzyme, heme oxygenase-1 (HO-1) was upregulated by D-4F. The Akt/AMPK/eNOS pathways were involved in the expression of HO-1 induced by D-4F. Moreover, the anti-oxidation, pro-proliferation, and pro-migration capacities of D-4F were diminished by the inhibitors of both eNOS (L-NAME) and HO-1 (Znpp). Additionally, downregulation of ATP-binding cassette transporter A1 (ABCA1) by siRNA abolished the activation of Akt, AMPK and eNOS, and reduced the upregulation of HO-1 triggered by D-4F. Furthermore, D-4F promoted the reendothelialization of injured intima in carotid artery injury model of C57BL/6J mice in vivo. In summary, these findings suggested that D-4F might be a powerful candidate in the protection of endothelial cells and the prevention of cardiovascular disease (CVD).

Cyclophilin A mediates the ox-LDL-induced activation and apoptosis of macrophages via autophagy

BACKGROUND

Oxidized low-density lipoprotein (ox-LDL) is the most common inflammatory factor that mediates the activation and apoptosis of macrophages. Cyclophilin A (CyPA) is expressed following oxidative stress, hypoxia, and infection. However, the role of CyPA in the activation and apoptosis of macrophages is unclear. The aims of the study were to determine whether CyPA mediates the ox-LDL-induced activation and apoptosis in RAW264.7 cells and to analyze potential mechanisms.

METHODS AND RESULTS

Through Western blot and ELISA test, the expression of CyPA induced by ox-LDL is time-dependent in RAW264.7 cells. Gene silencing of CyPA reduced the generation of lipid droplets in the cytoplasm and downregulated the expression of the surface markers of macrophage activation, namely, CD80, CD86, and major histocompatibility complex class 2 antigen. Cell apoptosis is significantly decreased and the level of anti-apoptosis protein bcl-2 is increased in CyPA silent cells compared with the control group. Finally, autophagy-related protein LC3-II/LC3-I ratio level significantly decreased in CyPA silent cells with less autophagosome formation while the blocked autophagy flux was recovered. The differences in the activation and apoptosis between CyPA silent cells and the control cells were inhibited by pre-treatment with class III PI 3-kinase inhibitor 3-MA.

CONCLUSIONS

These results indicate that CyPA mediates the ox-LDL-induced activation and apoptosis in RAW264.7 cells by regulating autophagy.

Oxidized high density lipoprotein induces macrophage apoptosis via toll-like receptor 4-dependent CHOP pathway

Oxidized HDL (ox-HDL), unlike native HDL that exerts antiatherogenic effects, plays a proatherogenic role. However, the underlying mechanisms are not completely understood. This study was designed to explore the inductive effect of ox-HDL on endoplasmic reticulum (ER) stress-CCAAT-enhancer-binding protein homologous protein (CHOP)-mediated macrophage apoptosis and its upstream mechanisms. Our results showed that ox-HDL could be ingested by macrophages, causing intracellular lipid accumulation. As with tunicamycin (an ER stress inducer), ox-HDL induced macrophage apoptosis with concomitant activation of ER stress pathway, including nuclear translocation of activating transcription factor 6, phosphorylation of protein kinase-like ER kinase and eukaryotic translation initiation factor 2α, and upregulation of glucose-regulated protein 78 and CHOP, which were inhibited by 4-phenylbutyric acid (PBA, an ER stress inhibitor) and CHOP gene silencing. Additionally, diphenyleneiodonium (DPI, an oxidative stress inhibitor), probucol (a reactive oxygen species scavenger), and toll-like receptor 4 (TLR4) silencing reduced ox-HDL-induced macrophage apoptosis, oxidative stress, and CHOP upregulation. Moreover, HDL isolated from patients with metabolic syndrome induced macrophage apoptosis, oxidative stress, and CHOP upregulation, which were blocked by PBA and DPI. These data indicate that ox-HDL may activate ER stress-CHOP-induced apoptotic pathway in macrophages via enhanced oxidative stress and that this pathway may be mediated by TLR4.

High-density lipoprotein mimetics: promises and challenges

The concept of lipoprotein mimetics was developed and extensively tested in the last three decades. Most lipoprotein mimetics were designed to recreate one or several functions of high-density lipoprotein (HDL) in the context of cardiovascular disease; however, the application of this approach is much broader. Lipoprotein mimetics should not just be seen as a set of compounds aimed at replenishing a deficiency or dysfunctionality of individual elements of lipoprotein metabolism but rather as a designer concept with remarkable flexibility and numerous applications in medicine and biology. In the present review, we discuss the fundamental design principles used to create lipoprotein mimetics, mechanisms of their action, medical indications and efficacy in animal models and human studies.

ORMDL3 contributes to the risk of atherosclerosis in Chinese Han population and mediates oxidized low-density lipoprotein-induced autophagy in endothelial cells

ORMDL sphingolipid biosynthesis regulator 3 (ORMDL3) is a universally confirmed susceptibility gene for asthma and has recently emerged as a crucial modulator in lipid metabolism, inflammation and endoplasmic reticulum (ER) stress-the mechanisms also closely involved in atherosclerosis (AS). Here we first presented the evidence of two single nucleotide polymorphisms regulating ORMDL3 expression (rs7216389 and rs9303277) significantly associated with AS risk and the evidence of increased ORMDL3 expression in AS cases compared to controls, in Chinese Han population. Following the detection of its statistical correlation with AS, we further explored the functional relevance of ORMDL3 and hypothesized a potential role mediating autophagy as autophagy is activated upon modified lipid, inflammation and ER stress. Our results demonstrated that in endothelial cells oxidized low-density lipoprotein (ox-LDL) up-regulated ORMDL3 expression and knockdown of ORMDL3 alleviated not only ox-LDL-induced but also basal autophagy. BECN1 is essential for autophagy initiation and silencing of ORMDL3 suppressed ox-LDL-induced as well as basal BECN1 expression. In addition, deletion of ORMDL3 resulted in greater sensitivity to ox-LDL-induced cell death. Taken together, ORMDL3 might represent a causal gene mediating autophagy in endothelial cells in the pathogenesis of AS.