Interleukin-10 down-regulates oxLDL induced expression of scavenger receptor A and Bak-1 in macrophages derived from THP-1 cells

Interaction between lipid metabolism and macrophage polarization in atherosclerosis

Atherosclerosis (AS) is a chronic inflammatory condition associated with lipid deposition. The interaction between abnormal lipid metabolism and the inflammatory response has been identified as the underlying cause of AS. Lipid metabolism disorders are considered the basis of atherosclerotic lesion formation and macrophages are involved in the entire process of AS formation. Macrophages have a high degree of plasticity, and the change of their polarization direction can determine the progress or regression of AS. The disturbances in bioactive lipid metabolism affect the polarization of different phenotypes of macrophages, thus, affecting lipid metabolism and the expression of key signal factors. Therefore, understanding the interaction between lipid metabolism and macrophages as well as their key targets is important for preventing and treating AS and developing new drugs. Recent studies have shown that traditional Chinese medicines play a positive role in the prevention and treatment of AS, providing a basis for clinical individualized treatment.

Enhanced autophagy and cholesterol efflux in mouse mesenchymal stem cells infected with H37Rv compared to H37Ra

Autophagy, metabolism, and associated signaling pathways play critical roles in bacterial survival within mammalian cells and influence the immunopathogenesis of infections. Mesenchymal stem cells (MSCs) are important host cells during Mycobacterium tuberculosis (Mtb) infection, yet how autophagy, metabolism, and related pathways are modulated in MSCs infected with the virulent H37Rv or the attenuated H37Ra strain of Mtb remains poorly understood. In this study, we utilized RNA-Seq screening, qRT-PCR, and Western Blotting to investigate the differences in these processes between H37Rv and H37Ra infections. Our results show that, at early time points (no more than 24h), infection with H37Rv significantly increased the expression of TlLR2, Prkaa2, and Prkaa2 phosphorylation in MSCs compared with H37Ra infection. Further analysis revealed that H37Rv infection induced a stronger autophagic response (evidenced by increased Atg9b and LC3II/LC3I) through the TLR2-AMP-AMPK pathway than H37Ra infection. Despite these differences in autophagy, there was no statistically significant difference in bacillary loads, suggesting that, in addition to autophagy, other factors such as apoptosis and immune-inflammatory responses may also regulate Mtb growth in MSCs. Additionally, the metabolic analysis showed that H37Rv infection led to increased expression of SLC2A3, PFKFB3, HK1, and ABCA1 in MSCs compared to H37Ra infection. These findings confirm that, during the early stages of infection, H37Rv induces enhanced autophagy, glucose metabolism, and cholesterol efflux through a more active TLR2-AMP-AMPK pathway than H37Ra. Therefore, MSCs may represent a novel target for the prevention and treatment of tuberculosis.

Comparative interleukins and chemokines analysis of mice mesenchymal stromal cells infected with Mycobacterium tuberculosis H37Rv and H37Ra

Inflammatory pathways involving Mesenchymal stromal cells (MSCs) play an important role in Mycobacterium tuberculosis (Mtb) infection. H37Rv (Rv) is a standard virulent strain, however, H37Ra (Ra) is a strain with reduced virulence. Interleukins and chemokines production are known to promote inflammation resistance in mammalian cells and is recently reported to regulate mycobacterial immunopathogenesis via inflammatory responses. MSCs are very important cells during Mtb infection. However, the different expressions of interleukins and chemokines in the process of Mtb-infected MSCs between Ra and Rv remain unclear. We used the techniques of RNA-Seq, Q-RT-PCR, ELISA, and Western Blotting. We have shown that Rv infection significantly increased mRNA expressions of Mndal, Gdap10, Bmp2, and Lif, thereby increasing more differentiation of MSCs compared with Ra infection in MSCs. Further investigation into the possible mechanisms, we found that Rv infection enhanced more inflammatory response (Mmp10, Mmp3, and Ptgs2) through more activation of the TLR2-MAP3K1-JNK pathway than did Ra infection in MSCs. Further action showed that Rv infection enhanced more Il1α, Il6, Il33, Cxcl2, Ccl3, and Ackr3 production than did Ra infection. Rv infection showed more expressions of Mmp10, Mmp3, Ptgs2, Il1α, Il6, Il33, Cxcl2, Ccl3, and Ackr3 possibly through more active TLR2-MAP3K1-JNK pathway than did Ra infection in MSCs. MSCs may therefore be a new candidate for the prevention and treatment of tuberculosis.

Monitoring Modified Lipoprotein Uptake and Macropinocytosis Associated with Macrophage Foam Cell Formation

Macrophage foam cell formation plays a crucial role in the initiation and progression of atherosclerosis. Macrophages uptake native and modified low density lipoprotein (LDL) through either receptor-dependent or receptor-independent mechanisms to transform into lipid laden foam cells. Foam cells are involved in the formation of fatty streak that is seen during the early stages of atherosclerosis development and therefore represents a promising therapeutic target. Normal or modified lipoproteins labeled with fluorescent dyes such as 1,1'-dioctadecyl-3-3-3',3'-tetramethylindocarbocyanine perchlorate (Dil) are often used to monitor their internalization during foam cell formation. In addition, the fluorescent dye Lucifer Yellow (LY) is widely used as a marker for macropinocytosis activity. In this chapter, we describe established methods for monitoring modified lipoprotein uptake and macropinocytosis during macrophage foam cell formation.

Scavenger Receptors as Biomarkers and Therapeutic Targets in Cardiovascular Disease

The process of atherosclerosis leads to the formation of plaques in the arterial wall, resulting in a decreased blood supply to tissues and organs and its sequelae: morbidity and mortality. A class of membrane-bound proteins termed scavenger receptors (SRs) are closely linked to the initiation and progression of atherosclerosis. Increasing interest in understanding SR structure and function has led to the idea that these proteins could provide new routes for cardiovascular disease diagnosis, management, and treatment. In this review, we consider the main classes of SRs that are implicated in arterial disease. We consider how our understanding of SR-mediated recognition of diverse ligands, including modified lipid particles, lipids, and carbohydrates, has enabled us to better target SR-linked functionality in disease. We also link clinical studies on vascular disease to our current understanding of SR biology and highlight potential areas that are relevant to cardiovascular disease management and therapy.

Sirtuin inhibits M. tuberculosis -induced apoptosis in macrophage through glycogen synthase kinase-3β

Apoptotic and inflammatory pathways play important roles in Mycobacterium tuberculosis-infected macrophages. Sirt1 is a member of the deacetylase family that is known to promote apoptosis resistance in mammalian cells and was recently reported to regulate mycobacterial immunopathogenesis via inflammatory responses. However, the apoptotic role of Sirt1 in the process of M. tuberculosis infection remains unclear. With the help of mouse peritoneal macrophage samples, we have shown that resveratrol, a Sirt1 activator, inhibited M. tuberculosis-induced apoptosis in peritoneal macrophages. Further, we found that Sirt1 activation prompted M. tuberculosis induced GSK3β phosphorylation. Further investigation into the possible mechanisms of action showed that Sirt1 directly interacted with GSK3β and enhanced GSK3β phosphorylation by promoting its deacetylation. Sirt1 activation inhibited M. tuberculosis growth. Thus, it seemed that Sirt1 acted as a novel regulator of apoptosis signaling in M. tuberculosis infection via its direct effects on GSK3β. Sirt1 may therefore be a new candidate for the prevention and treatment of tuberculosis.

IL-33 promotes IL-10 production in macrophages: a role for IL-33 in macrophage foam cell formation

We evaluated the role of IL-10- in IL-33-mediated cholesterol reduction in macrophage-derived foam cells (MFCs) and the mechanism by which IL-33 upregulates IL-10. Serum IL-33 and IL-10 levels in coronary artery disease patients were measured. The effects of IL-33 on intra-MFC cholesterol level, IL-10, ABCA1 and CD36 expression, ERK 1/2, Sp1, STAT3 and STAT4 activation, and IL-10 promoter activity were determined. Core sequences were identified using bioinformatic analysis and site-specific mutagenesis. The serum IL-33 levels positively correlated with those of IL-10. IL-33 decreased cellular cholesterol level and upregulated IL-10 and ABCA1 but had no effect on CD36 expression. siRNA-IL-10 partially abolished cellular cholesterol reduction and ABCA1 elevation by IL-33 but did not reverse the decreased CD36 levels. IL-33 increased IL-10 mRNA production but had little effect on its stability. IL-33 induced ERK 1/2 phosphorylation and increased the luciferase expression driven by the IL-10 promoter, with the highest extent within the −2000 to −1752 bp segment of the 5′-flank of the transcription start site; these effects were counteracted by U0126. IL-33 activated Sp1, STAT3 and STAT4, but only the STAT3 binding site was predicted in the above segment. Site-directed mutagenesis of the predicted STAT3-binding sites (CTGCTTCCTGGCAGCAGAA→CTGCCTGGCAGCAGAA) reduced luciferase activity, and a STAT3 inhibitor blocked the regulatory effects of IL-33 on IL-10 expression. Chromatin immunoprecipitation (CHIP) confirmed the STAT3-binding sequences within the −1997 to −1700 and −1091 to −811 bp locus regions. IL-33 increased IL-10 expression in MFCs via activating ERK 1/2 and STAT3, which subsequently promoted IL-10 transcription and thus contributed to the beneficial effects of IL-33 on MFCs.

Sugar-based amphiphilic polymers for biomedical applications: from nanocarriers to therapeutics

Various therapeutics exhibit unfavorable physicochemical properties or stability issues that reduce their in vivo efficacy. Therefore, carriers able to overcome such challenges and deliver therapeutics to specific in vivo target sites are critically needed. For instance, anticancer drugs are hydrophobic and require carriers to solubilize them in aqueous environments, and gene-based therapies (e.g., siRNA or pDNA) require carriers to protect the anionic genes from enzymatic degradation during systemic circulation. Polymeric micelles, which are self-assemblies of amphiphilic polymers (APs), constitute one delivery vehicle class that has been investigated for many biomedical applications. Having a hydrophobic core and a hydrophilic shell, polymeric micelles have been used as drug carriers. While traditional APs are typically comprised of nondegradable block copolymers, sugar-based amphiphilic polymers (SBAPs) synthesized by us are comprised of branched, sugar-based hydrophobic segments and a hydrophilic poly(ethylene glycol) chain. Similar to many amphiphilic polymers, SBAPs self-assemble into polymeric micelles. These nanoscale micelles have extremely low critical micelle concentrations offering stability against dilution, which occurs with systemic administration. In this Account, we illustrate applications of SBAPs for anticancer drug delivery via physical encapsulation within SBAP micelles and chemical conjugation to form SBAP prodrugs capable of micellization. Additionally, we show that SBAPs are excellent at stabilizing liposomal delivery systems. These SBAP-lipid complexes were developed to deliver hydrophobic anticancer therapeutics, achieving preferential uptake in cancer cells over normal cells. Furthermore, these complexes can be designed to electrostatically complex with gene therapies capable of transfection. Aside from serving as a nanocarrier, SBAPs have also demonstrated unique bioactivity in managing atherosclerosis, a major cause of cardiovascular disease. The atherosclerotic cascade is usually triggered by the unregulated uptake of oxidized low-density lipoprotein, a cholesterol carrier, in macrophages of the blood vessel wall; SBAPs can significantly inhibit oxidized low-density lipoprotein uptake in macrophages and abrogate the atherosclerotic cascade. By modification of various functionalities (e.g., branching, stereochemistry, hydrophobicity, and charge) in the SBAP chemical structure, SBAP bioactivity was optimized, and influential structural components were identified. Despite the potential of SBAPs as atherosclerotic therapies, blood stability of the SBAP micelles was not ideal for in vivo applications, and means to stabilize them were pursued. Using kinetic entrapment via flash nanoprecipitation, SBAPs were formulated into nanoparticles with a hydrophobic solute core and SBAP shell. SBAP nanoparticles exhibited excellent physiological stability and enhanced bioactivity compared with SBAP micelles. Further, this method enables encapsulation of additional hydrophobic drugs (e.g., vitamin E) to yield a stable formulation that releases two bioactives. Both as nanoscale carriers and as polymer therapeutics, SBAPs are promising biomaterials for medical applications.

Immunological aspects of atherosclerosis

Atherosclerosis is a complex chronic inflammatory and metabolic disease that involves the collaboration of several cellular components of the immune system and results in thickening of the arterial wall. Atherosclerosis is also the primary cause of coronary artery and cerebrovascular diseases. A multitude of immune cell subsets, soluble molecules such as chemokines and cytokines, and circulating lipids play pivotal roles in atherosclerosis development. In this review, we highlight the role of the immune system in the course of atherosclerotic disease development and discuss the mechanisms involved.

Role of protein kinase C δ in ER stress and apoptosis induced by oxidized LDL in human vascular smooth muscle cells

During atherogenesis, excess amounts of low-density lipoproteins (LDL) accumulate in the subendothelial space where they undergo oxidative modifications. Oxidized LDL (oxLDL) alter the fragile balance between survival and death of vascular smooth muscle cells (VSMC) thereby leading to plaque instability and finally to atherothrombotic events. As protein kinase C δ (PKCδ) is pro-apoptotic in many cell types, we investigated its potential role in the regulation of VSMC apoptosis induced by oxLDL. We found that human VSMC silenced for PKCδ exhibited a protection towards oxLDL-induced apoptosis. OxLDL triggered the activation of PKCδ as shown by its phosphorylation and nuclear translocation. PKCδ activation was dependent on the reactive oxygen species generated by oxLDL. Moreover, we demonstrated that PKCδ participates in oxLDL-induced endoplasmic reticulum (ER) stress-dependent apoptotic signaling mainly through the IRE1α/JNK pathway. Finally, the role of PKCδ in the development of atherosclerosis was supported by immunohistological analyses showing the colocalization of activated PKCδ with ER stress and lipid peroxidation markers in human atherosclerotic lesions. These findings highlight a role for PKCδ as a key regulator of oxLDL-induced ER stress-mediated apoptosis in VSMC, which may contribute to atherosclerotic plaque instability and rupture.

Bisoprolol reverses epinephrine-mediated inhibition of cell emigration through increases in the expression of β-arrestin 2 and CCR7 and PI3K phosphorylation, in dendritic cells loaded with cholesterol

The effect of bisoprolol on dendritic cell (DC) migration was investigated, including the analysis of protein expression, cytokine secretion and activation of the PI3K-pathway. The chemotactic cell numbers in cholesterol-loaded DCs treated with epinephrine were significantly decreased by 26.66±6.29% (6h), 35.67±2.91% (12h) and 29.33±1.09% (24h). This effect was significantly reversed by 46.00±10.65% (6h), 64.25±6.77% (12h) and 55.74±5.51% (24h) when bisoprolol and epinephrine were both present. In cholesterol-loaded DCs, treatment with epinephrine significantly increased AR-β1 protein expression by 56.99±4.87%, but inhibited β-arrestin 2 and CCR7 protein expression by 30.51±4.22% and 25.31±0.04%, respectively. These effects were reversed by bisoprolol by 36.87±4.40%, 41.47±3.95% and 30.14±0.54%, respectively. TNF-α and MMP9 levels were decreased by 68.33±4.00% and 39.57±9.21% in cholesterol-loaded DCs treated with epinephrine. In contrast, when bisoprolol and epinephrine were administered together, the secretion of these proteins was significantly increased by 233.81±37.06 % and 76.66±14.21%, respectively. Treatment with epinephrine decreased PI3K-phosphorylation by 31.88±2.79%, 40.24±5.69% and 30.93±4.66% at 15, 30 and 60min, respectively, whereas the effect of epinephrine on the expression of phosphorylated PI3K was reversed by 49.49±12.12%, 70.93±16.14% and 47.62±6.00%, respectively, when cells were treated with both bisoprolol and epinephrine. Wortmannin inhibited the effects of bisoprolol on PI3K-phosphorylation (38.63±6.12%), the expression of CCR7 (23.4±2.72%), the secretion of TNF-α (69.46±4.48%) and MMP9 (43.15±4.63%), and the number of chemotactic cells (36.84±5.22%). This is the first study to establish a signaling pathway, epinephrine-AR-β1-β-arrestin2-PI3K-MMP9/CCR7, which plays a critical role in the migration of DCs.