Oxysterols induce transition of monocytic cells to phenotypically mature dendritic cell-like cells

Oxysterols in tumor immune microenvironment (TIME)

Oxysterols are compounds generated through oxidative reactions involving cholesterol and other steroid molecules. They play a crucial role in the tumor immune microenvironment by interacting with molecules such as the cell membrane receptor EBI2 and nuclear receptors like LXR and PXR. This interaction regulates immune cell signaling pathways, affecting proliferation, apoptosis, migration, and invasion in tumor-related processes. Activating these receptors alters the function and behavior of immune cells-such as macrophages, T cells, and dendritic cells-within the tumor microenvironment, thus promoting or inhibiting tumor development. Certain oxidized steroids can increase both the number and activation of infiltrating T cells, synergizing with anti-PD-1 to enhance anti-tumor efficacy. An in-depth study of the biological mechanisms of oxidized sterols will not only enhance our understanding of the complexity of the tumor immune microenvironment but may also reveal new therapeutic targets, providing innovative strategies for tumor immunotherapy.

Immune Implications of Cholesterol-Containing Lipid Nanoparticles

The majority of clinically approved nanoparticle-mediated therapeutics are lipid nanoparticles (LNPs), and most of these LNPs are liposomes containing cholesterol. LNP formulations significantly alter the drug pharmacokinetics (PK) due to the propensity of nanoparticles for uptake by macrophages. In addition to readily engulfing LNPs, the high expression of cholesterol hydroxylases and reactive oxygen species (ROS) in macrophages suggests that they will readily produce oxysterols from LNP-associated cholesterol. Oxysterols are a heterogeneous group of cholesterol oxidation products that have potent immune modulatory effects. Oxysterols are implicated in the pathogenesis of atherosclerosis and certain malignancies; they have also been found in commercial liposome preparations. Yet, the in vivo metabolic fate of LNP-associated cholesterol remains unclear. We review herein the mechanisms of cellular uptake, trafficking, metabolism, and immune modulation of endogenous nanometer-sized cholesterol particles (i.e., lipoproteins) that are also relevant for cholesterol-containing nanoparticles. We believe that it would be imperative to better understand the in vivo metabolic fate of LNP-associated cholesterol and the immune implications for LNP-therapeutics. We highlight critical knowledge gaps that we believe need to be addressed in order to develop safer and more efficacious lipid nanoparticle delivery systems.

Oxysterol Induces Expression of 60 kDa Chaperone Protein on Cell Surface of Microglia

Microglia, essential immune cells in the brain, play crucial roles in neuroinflammation by performing various functions such as neurogenesis, synaptic pruning, and pathogen defense. These cells are activated by inflammatory factors like β-amyloid (Aβ) and oxysterols, leading to morphological and functional changes, including the secretion of inflammatory cytokines and the upregulation of MHC class II molecules. This study focused on identifying specific markers for microglial activation, with a particular emphasis on the roles of oxysterols in this process. We used the HMC3 human microglial cell line to investigate the induction of heat shock protein 60 (HSP60), a chaperonin protein by oxysterols, specifically in the presence of 25-hydroxycholesterol (25OHChol) and 27-hydroxycholesterol (27OHChol). Our findings obtained by the proteomics approach revealed that these oxysterols significantly increased HSP60 expression on microglial cells. This induction was further confirmed using Western blot analysis and immunofluorescence microscopy. Additionally, Aβ1-42 also promoted HSP60 expression, indicating its role as a microglial activator. HSP60 involved in protein folding and immune modulation was identified as a potential marker for microglial activation. This study underscores the importance of HSP60 in the inflammatory response of microglia, suggesting its utility as a target for new therapeutic approaches in neuroinflammatory diseases such as Alzheimer's disease (AD).

Immunometabolism in the pathogenesis of asthma

Bronchial asthma is a heterogeneous disease characterised by chronic airway inflammation. A variety of immune cells such as eosinophils, mast cells, T lymphocytes, neutrophils and airway epithelial cells are involved in the airway inflammation and airway hyperresponsiveness in asthma pathogenesis, resulting in extensive and variable reversible expiratory airflow limitation. However, the precise molecular mechanisms underlying the allergic immune responses, particularly immunometabolism, remains unclear. Studies have detected enhanced oxidative stress, and abnormal metabolic progresses of glycolysis, fatty acid and amino acid in various immune cells, inducing dysregulation of innate and adaptive immune responses in asthma pathogenesis. Immunometabolism mechanisms contain multiple signalling pathways, providing novel therapy targets for asthma. This review summarises the current knowledge on immunometabolism reprogramming in asthma pathogenesis, as well as potential therapy strategies.

Targeted Mevalonate Pathway and Autophagy in Antitumor Immunotherapy

Tumors of the digestive system are currently one of the leading causes of cancer-related death worldwide. Despite considerable progress in tumor immunotherapy, the prognosis for most patients remains poor. In the tumor microenvironment (TME), tumor cells attain immune escape through immune editing and acquire immune tolerance. The mevalonate pathway and autophagy play important roles in cancer biology, antitumor immunity, and regulation of the TME. In addition, there is metabolic crosstalk between the two pathways. However, their role in promoting immune tolerance in digestive system tumors has not previously been summarized. Therefore, this review focuses on the cancer biology of the mevalonate pathway and autophagy, the regulation of the TME, metabolic crosstalk between the pathways, and the evaluation of their efficacy as targeted inhibitors in clinical tumor immunotherapy.

Targeting cholesterol metabolism in Cancer: From molecular mechanisms to therapeutic implications

Cholesterol is an essential component of cell membranes and helps to maintain their structure and function. Abnormal cholesterol metabolism has been linked to the development and progression of tumors. Changes in cholesterol metabolism triggered by internal or external stimuli can promote tumor growth. During metastasis, tumor cells require large amounts of cholesterol to support their growth and colonization of new organs. Recent research has shown that cholesterol metabolism is reprogrammed during tumor development, and this can also affect the anti-tumor activity of immune cells in the surrounding environment. However, identifying the specific targets in cholesterol metabolism that regulate cancer progression and the tumor microenvironment is still a challenge. Additionally, exploring the potential of combining statin drugs with other therapies for different types of cancer could be a worthwhile avenue for future drug development. In this review, we focus on the molecular mechanisms of cholesterol and its derivatives in cell metabolism and the tumor microenvironment, and discuss specific targets and relevant therapeutic agents that inhibit aspects of cholesterol homeostasis.

Side-Chain Immune Oxysterols Induce Neuroinflammation by Activating Microglia

In individuals with Alzheimer's disease, the brain exhibits elevated levels of IL-1β and oxygenated cholesterol molecules (oxysterols). This study aimed to investigate the effects of side-chain oxysterols on IL-1β expression using HMC3 microglial cells and ApoE-deficient mice. Treatment of HMC3 cells with 25-hydroxycholesterol (25OHChol) and 27-hydroxycholesterol (27OHChol) led to increased IL-1β expression at the transcript and protein levels. Additionally, these oxysterols upregulated the surface expression of MHC II, a marker of activated microglia. Immunohistochemistry performed on the mice showed increased microglial expression of IL-1β and MHC II when fed a high-cholesterol diet. However, cholesterol and 24s-hydroxycholesterol did not increase IL-1β transcript levels or MHC II expression. The extent of IL-1β increase induced by 25OHChol and 27OHChol was comparable to that caused by oligomeric β-amyloid, and the IL-1β expression induced by the oxysterols was not impaired by polymyxin B, which inhibited lipopolysaccharide-induced IL-1β expression. Both oxysterols enhanced the phosphorylation of Akt, ERK, and Src, and inhibition of these kinase pathways with pharmacological inhibitors suppressed the expression of IL-1β and MHC II. The pharmacological agents chlorpromazine and cyclosporin A also impaired the oxysterol-induced expression of IL-1β and upregulation of MHC II. Overall, these findings suggest that dysregulated cholesterol metabolism leading to elevated levels of side-chain oxysterols, such as 25OHChol and 27OHChol, can activate microglia to secrete IL-1β through a mechanism amenable to pharmacologic intervention. The activation of microglia and subsequent neuroinflammation elicited by the immune oxysterols can contribute to the development of neurodegenerative diseases.

A decision support system based on artificial intelligence and systems biology for the simulation of pancreatic cancer patient status

Oncology treatments require continuous individual adjustment based on the measurement of multiple clinical parameters. Prediction tools exploiting the patterns present in the clinical data could be used to assist decision making and ease the burden associated to the interpretation of all these parameters. The goal of this study was to predict the evolution of patients with pancreatic cancer at their next visit using information routinely recorded in health records, providing a decision-support system for clinicians. We selected hematological variables as the visit's clinical outcomes, under the assumption that they can be predictive of the evolution of the patient. Multivariate models based on regression trees were generated to predict next-visit values for each of the clinical outcomes selected, based on the longitudinal clinical data as well as on molecular data sets streaming from in silico simulations of individual patient status at each visit. The models predict, with a mean prediction score (balanced accuracy) of 0.79, the evolution trends of eosinophils, leukocytes, monocytes, and platelets. Time span between visits and neutropenia were among the most common factors contributing to the predicted evolution. The inclusion of molecular variables from the systems-biology in silico simulations provided a molecular background for the observed variations in the selected outcome variables, mostly in relation to the regulation of hematopoiesis. In spite of its limitations, this study serves as a proof of concept for the application of next-visit prediction tools in real-world settings, even when available data sets are small.

Atheroma-Relevant 7-Oxysterols Differentially Upregulate Cd14 Expression

The expression of CD14 in monocytic cells is elevated in atherosclerotic lesions where 7-oxyterols are abundant. However, it remains unknown whether atheroma-relevant 7-oxysterols are involved in receptor expression. Therefore, we investigated the effects of 7α-hydroxycholesterol (7αOHChol), 7β-hydroxycholesterol (7βOHChol), and 7-ketocholesterol (7K) on CD14 levels in THP-1 cells. The three 7-oxysterols increased CD14 transcript levels at a distinct time point, elevated cellular CD14 protein levels, and promoted the release of soluble CD (sCD14) from THP-1 cells. Our data revealed that CD14 expression was most strongly induced after treatment with 7αOHChol. Moreover, 7αOHChol alone upregulated membrane-bound CD14 levels and enhanced responses to lipopolysaccharides, as determined by CCL2 production and monocytic cell migration. The 7-oxysterols also increased the gelatinolytic activity of MMP-9, and a cell-permeable, reversible MMP-9 inhibitor, MMP-9 inhibitor I, significantly impaired sCD14 release. These results indicate that 7-oxysterols differentially induce CD14 expression in vascular cells and contribute to the monocytic cell expression of CD14 via overlapping, but distinct, mechanisms.

27-Hydroxycholesterol induces expression of zonula occludens-1 in monocytic cells via multiple kinases pathways

Zonula occludens (ZO)-1, a tight-junction protein (TJP), is expressed in dendritic cells (DCs) but not in monocytes, and 27-hydroxycholesterol (27OHChol) drives the differentiation of monocytes into DCs. Because the effects of 27OHChol on ZO-1 are not yet clearly defined, we investigated whether 27OHChol induces expression of the TJP. The treatment of human THP-1 monocytic cells with 27OHChol resulted in the elevated transcript levels of ZO-1 but not of ZO-2 or -3. 27OHChol increased the total amount of ZO-1 protein in the cells as well as its level on the cells surface. Cholesterol, however, did not influence expression of ZO-1. And, the expression of ZO-1 protein was mediated by endoplasmic reticulum (ER)-to-Golgi body transport system. Pharmacological kinase inhibition with LY294002 (a PI3K inhibitor), U0126 (a MEK/ERK inhibitor), or PP2 (a Src family kinase inhibitor) resulted in impaired ZO-1 expression at both transcript and protein levels. Drugs that are reported to suppress DC differentiation also inhibited 27OHChol-mediated expression and the localization of ZO-1, indicating the coincidence of ZO-1 upregulation and DC differentiation. These results suggest that ZO-1 is differentially expressed while monocytes differentiate into DCs in the presence of 27OHChol via pathways in which distinct signaling molecules are involved.

Miconazole Suppresses 27-Hydroxycholesterol-induced Inflammation by Regulating Activation of Monocytic Cells to a Proinflammatory Phenotype

Miconazole is effective in treating inflammatory skin conditions and has well-established antifungal effects. To elucidate the underlying mechanisms mediating its additional beneficial effects, we assessed whether miconazole influences the inflammation induced by 27-hydroxycholesterol (27OHChol), an oxygenated cholesterol derivative with high proinflammatory activity, using THP-1 monocytic cells. Miconazole dose-dependently inhibited the expression of proinflammatory markers, including CCL2 and CCR5 ligands such as CCL3 and CCL4, and impaired the migration of monocytic cells and CCR5-positive T cells. In the presence of 27OHChol, miconazole decreased CD14 surface levels and considerably weakened the lipopolysaccharide response. Furthermore, miconazole blocked the release of soluble CD14 and impaired the transcription of the matrix metalloproteinase-9 gene and secretion of its active gene product. Additionally, it downregulated the expression of ORP3 and restored the endocytic function of THP-1 cells. Collectively, these findings indicate that miconazole regulates the 27OHChol-induced expression of proinflammatory molecules in monocytic cells, thereby suppressing inflammation in an oxysterol-rich milieu.

Cholesterol metabolism: a new molecular switch to control inflammation

The immune system protects the body against harm by inducing inflammation. During the immune response, cells of the immune system get activated, divided and differentiated in order to eliminate the danger signal. This process relies on the metabolic reprogramming of both catabolic and anabolic pathways not only to produce energy in the form of ATP but also to generate metabolites that exert key functions in controlling the response. Equally important to mounting an appropriate effector response is the process of immune resolution, as uncontrolled inflammation is implicated in the pathogenesis of many human diseases, including allergy, chronic inflammation and cancer. In this review, we aim to introduce the reader to the field of cholesterol immunometabolism and discuss how both metabolites arising from the pathway and cholesterol homeostasis are able to impact innate and adaptive immune cells, staging cholesterol homeostasis at the centre of an adequate immune response. We also review evidence that demonstrates the clear impact that cholesterol metabolism has in both the induction and the resolution of the inflammatory response. Finally, we propose that emerging data in this field not only increase our understanding of immunometabolism but also provide new tools for monitoring and intervening in human diseases, where controlling and/or modifying inflammation is desirable.

Trend of 25-hydroxycholesterol and 27-hydroxycholesterol plasma levels in patients affected by active chronic hepatitis B virus infection and inactive carriers

Hepatitis B virus (HBV) infection is a global health problem with different immunological phases and therapeutic approaches. The serological condition of inactive carrier (IC) was recently well defined as a clinical and virological stable status, in which specific treatment is usually deferred, while the active chronic hepatitis B (CHB) condition requires an immediate treatment strategy. Recently, a possible broad antiviral effect of oxysterols, in particular 25-hydroxycholesterol (25OHC) and 27-hydroxycholesterol (27OHC), was observed, as most likely linked to the positive modulation of innate immunity, but no clear evidence is available about their possible role in chronic HBV infection. Thus, we examined the relationship between the plasma levels of oxysterols and the disease condition of 40 HBV patients, without treatment at the start of the study. Of these, 33 were ICs and 7 were active CHB subjects. A marked reduction of 25OHC and 27OHC plasma levels was detectable in all active CHB recruited patients, while the plasma values observed in ICs all remained within the physiological range. No difference was observed between the two groups of patients with regard to the plasma levels of 24-hydroxycholesterol (24OHC). Further, the plasma level of 27OHC ≥ 140 μg/L was shown to be predictive of an inactive carrier status. This cohort study points to 27OHC as a good candidate biomarker to differentiate active and inactive CHB status. An increasing bulk of research reports is supporting the very likely contribution of this oxysterol to the immunological control of chronic hepatitis B.

Role of 27-hydroxycholesterol and its metabolism in cancer progression: Human studies

Direct translation of findings achieved in experimental cell or animal models to humans is quite a difficult task. We focused here only on the epidemiological and ex vivo human studies so far available about the role of 27-hydroxycholesterol (27OHC) and related metabolism in cancer development. Some studies point to an adverse effect of 27OHC in breast cancer, based on the oxysterol's recognized ability to bind to and modulate estrogen receptors. The detrimental role of this side chain oxysterol would be evident in cancer progression, mainly in post-menopausal women and in an advanced stage of the disease. Other human researches, however, would rather correlate 27OHC intra-tumoral levels to a better prognosis. The analyses on human prostate cancer specimens performed to date are all against a detrimental contribution of 27OHC, rather suggesting interesting anti-prostate cancer effects exerted by this oxysterol. Finally, an increased 27OHC synthesis on the contrary seems to favour progression of late stage cancers in colon, brain and thyroid tissues, as found for breast cancer, possibly due to pro-inflammatory and pro-survival signalling triggered by disproportionate amounts of this oxysterol.

Lipid metabolism in asthma: Immune regulation and potential therapeutic target

Asthma is a chronic inflammatory disease of the lungs that poses a considerable health and socioeconomic burden. Several risk factors work synergistically to affect the progression of asthma. Lipid metabolism, especially in distinct cells such as T cells, macrophages, granulocytes, and non-immune cells, plays an essential role in the pathogenesis of asthma, as lipids are potent signaling molecules that regulate a multitude of cellular response. In this review, we focused on the metabolic pathways of lipid molecules, especially fatty acids and their derivatives, and summarized their roles in various cells during the pathogenesis of asthma along with the current pharmacological agents targeting lipid metabolism.

27-Hydroxycholesterol induces macrophage gene expression via LXR-dependent and -independent mechanisms

27-Hydroxycholesterol (27OHChol) exhibits agonistic activity for liver X receptors (LXRs). To determine roles of the LXR agonistic activity in macrophage gene expression, we investigated the effects of LXR inhibition on the 27OHChol-induced genes. Treatment of human THP-1 cells with GSK 2033, a potent cell-active LXR antagonist, results in complete inhibition in the transcription of LXR target genes (such as LXRα and ABCA1) induced by 27OHChol or a synthetic LXR ligand TO 901317. Whereas expression of CCL2 and CCL4 remains unaffected by GSK 2033, TNF-α expression is further induced and 27OHChol-induced CCL3 and CXCL8 genes are suppressed at both the transcriptional and protein translation levels in the presence of GSK 2033. This LXR antagonist downregulates transcript levels and surface expression of CD163 and CD206 and suppresses the transcription of CD14, CD80, and CD86 genes without downregulating their surface levels. GSK 2033 alone had no effect on the basal expression levels of the aforementioned genes. Collectively, these results indicate that LXR inhibition leads to differential regulation of 27-hydroxycholesterol-induced genes in macrophages. We propose that 27OHChol induces gene expression and modulates macrophage functions via LXR-dependent and -independent mechanisms.

Effect of industrial processing and storage procedures on oxysterols in milk and milk products

Oxysterols are products of enzymatic and/or chemical cholesterol oxidation. While some of the former possess broad antiviral activities, the latter mostly originate from the deterioration of the nutritional value of foodstuff after exposure to heat, light, radiation and oxygen, raising questions about their potential health risks. We evaluated the presence of selected oxysterols in bovine colostrum and monitored the evolution of their cholesterol ratio throughout an entire industrial-scale milk production chain and after industrially employed storage procedures of milk powders. We report here for the first time the presence of high levels of the enzymatic oxysterol 27-hydroxycholesterol (27OHC) in concentrations of antiviral interest in bovine colostrum (87.04 ng mL^-1) that decreased during the first postpartum days (56.35 ng mL^-1). Of note, this oxysterol is also observed in milk and milk products and is not negatively affected by industrial processing or storage. We further highlight an exponential increase of the non-enzymatic oxysterols 7β-hydroxycholesterol (7βOHC) and 7-ketocholesterol (7KC) in both whole (WMPs) and skimmed milk powders (SMPs) during prolonged storage, confirming their role as reliable biomarkers of cholesterol oxidation over time: after 12 months, 7βOHC reached in both SMPs and WMPs amounts that have been found to be potentially toxic in vitro (265.46 ng g^-1 and 569.83 ng g^-1, respectively). Interestingly, industrial processes appeared to affect the generation of 7βOHC and 7KC differently, depending on the presence of fat in the product: while their ratios increased significantly after skimming and processing of skimmed milk and milk products, this was not observed after processing whole milk and milk cream.

The cholesterol metabolite 27-hydroxycholesterol inhibits SARS-CoV-2 and is markedly decreased in COVID-19 patients

There is an urgent need to identify antivirals against the coronavirus SARS-CoV-2 in the current COVID-19 pandemic and to contain future similar emergencies early on. Specific side-chain cholesterol oxidation products of the oxysterols family have been shown to inhibit a large variety of both enveloped and non-enveloped human viral pathogens. Here we report on the in vitro inhibitory activity of the redox active oxysterol 27-hydroxycholesterol against SARS-CoV-2 and against one of the common cold agents HCoV-OC43 human coronavirus without significant cytotoxicity. Interestingly, physiological serum levels of 27-hydroxycholesterol in SARS-CoV-2 positive subjects were significantly decreased compared to the matched control group, reaching a marked 50% reduction in severe COVID-19 cases. Moreover, no correlation at all was observed between 24-hydroxycholesterol and 25-hydroxycholesterol serum levels and the severity of the disease. Opposite to that of 27-hydroxycholesterol was the behaviour of two recognized markers of redox imbalance, i.e. 7-ketocholesterol and 7β-hydroxycholesterol, whose serum levels were significantly increased especially in severe COVID-19. The exogenous administration of 27-hydroxycholesterol may represent in the near future a valid antiviral strategy in the worsening of diseases caused by present and emerging coronaviruses.

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27-hydroxycholesterol (27OHC) inhibits the replication of SARS-CoV-2 by interfering with its entry into target cells.

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The broad antiviral effect of 27OHC is also exerted against another β-coronavirus, HCoV-OC43.

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Blood levels of 27OHC were decreased in SARS-CoV-2 infected individuals, especially in patients with severe COVID-19.

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COVID-19 patients showed increased serum levels of 7-ketocholesterol and 7β-hydroxycholesterol, markers of oxidative stress.

Reblastatins Inhibit Phenotypic Changes of Monocytes/Macrophages in a Milieu Rich in 27-Hydroxycholesterol

We investigated effects of reblastatins on phenotypic changes in monocytes/macrophages induced by 27-hydroxycholesterol (27OHChol). Treatment of THP-1 monocytic cells with reblastatin derivatives, such as 17-demethoxy-reblastatin (17-DR), 18-dehydroxyl-17-demethoxyreblastatin (WK88-1), 18-hydroxyl-17-demethoxyreblastatin (WK88-2), and 18-hydroxyl-17-demethoxy-4,5-dehydroreblastatin (WK88-3), resulted in blockage of CCL2, CCL3, and CCL4 expression at the transcription and protein levels, which, in turn, impaired migration of monocytes/macrophages and Jurkat T cells expressing CCR5, and almost complete inhibition of transcription of M1 marker cytokines, like CXCL10, CXCL11, and TNF-α. Reblastatins also downregulated surface CD14 as well as soluble CD14 along with inhibition of LPS response and matrix metalloprotease-9 expression. Surface levels of mature dendritic cell (mDC)-specific markers, including CD80, CD83, CD88, CD197, and MHC class I and II molecules, were remarkably down-regulated, and 27OHChol-induced decrease of endocytic activity was recovered following treatment with 17-DR, WK88-1, WK88-2, and WK88-3. However, 15-hydroxyl-17-demethoxyreblastatin (DHQ3) did not affect the molecular or functional changes in monocytic cells induced by 27OHChol. Furthermore, surface levels of CD105, CD137, and CD166 were also down-regulated by 17-DR, WK88-1, WK88-2, and WK88-3, but not by DHQ3. Collectively, results of the current study indicate that, except DHQ3, reblastatins regulate the conversion and differentiation of monocytic cells to an immunostimulatory phenotype and mDCs, respectively, which suggests possible applications of reblastatins for immunomodulation in a milieu rich in oxygenated cholesterol molecules.

Prednisolone suppresses the immunostimulatory effects of 27-hydroxycholesterol

In cholesterol-fed rabbits, site-specific targeting of prednisolone nanoparticles results in significantly reduced neo-intimal inflammation with a decreased infiltration of monocytes/macrophages. To understand the molecular mechanisms underlying this, the current study investigated whether prednisolone affects the immune attributes of 27-hydroxycholesterol (27OHChol), the major oxidized cholesterol molecule in circulation and tissue, in human (THP-1) monocyte/macrophage cells. THP-1 cells were exposed to 27OHChol in the presence of prednisolone followed by evaluation of inflammatory molecules at mRNA and protein levels by quantitative PCR, western blotting, ELISA and flow cytometry. The results revealed that prednisolone suppressed the 27OHChol-mediated expression of various macrophage (M)1 markers, including chemokine ligand 2, C-X-C chemokine motif 10, tumor necrosis factor-α and CD80. Treatment also impaired the 27OHCHol-enhanced migration of monocytic cells, downregulated the 27OHChol-induced cell surface expression of CD14 and inhibited the release of soluble CD14 comparable with a weakened lipopolysaccharide response. Furthermore, prednisolone suppressed the 27OHChol-induced expression of matrix metalloproteinase 9 at the transcriptional and protein level, as well as the phosphorylation of the p65 subunit. Prednisolone increased the transcription of CD163 and CD206 genes, and augmented the 27OHChol-induced transcription of CD163 without upregulating the 27OHChol-induced surface protein level of the gene. The results indicated that prednisolone inhibited the polarization of monocytes/macrophages towards the M1 phenotype, which that the immunostimulatory effects of 27OHCHol were being regulated and the immune responses in conditions that were rich in oxygenated cholesterol molecules were being modulated.

7-Oxygenated cholesterol molecules differentially affect the expression of zonula occludens-1 in vascular smooth muscle cells and monocyte/macrophage cells

To investigate the effects of 7-oxygenated cholesterol molecules on the expression of tight junction proteins, we examined the outcomes effects of 7-ketocholesterol (7K), 7α-hydroxycholesterol (7αOHChol) and 7β-hydroxycholesterol (7βOHChol) on the expression of the tight-junction protein zonula occludens-1 (ZO-1) using vascular cells. Vascular smooth muscle cells (VSMCs) constitutively express ZO-1, and this expression remained unaffected in the presence of cholesterol. However, the level of ZO-1 protein decreased after exposure to 7K and, to a lesser extent, 7αOHChol and 7βOHChol. ZO-1 was translocated to the nucleus following treatment with 7K; this translocation was inhibited by z-VAD-fmk, a pan-caspase inhibitor. ZO-1 protein was found to disintegrate in the aorta of ApoE knockout mice fed a high cholesterol diet, whereas it remained intact in the wild-type control. THP-1 monocyte/macrophage cells, which show no expression of ZO-1, were not influenced by treatment with cholesterol, 7K, and 7βOHChol. However, the treatment of THP-1 cells with 7αOHChol resulted in ZO-1 expression, which largely remained localized on the cytoplasmic membrane. These results indicate the varying effects of 7-oxygenated cholesterol molecules on the expression and localization of ZO-1 depending on cell types, and suggest the contribution of 7-oxygeneted cholesterol molecules to the structural alteration of tight junctions.

27-Hydroxycholesterol upregulates the production of heat shock protein 60 of monocytic cells

Investigating differentially expressed proteins in a milieu rich in cholesterol oxidation products, we found via mass spectrometry-based proteomics that surface levels of heat shock protein 60 (HSP60) were upregulated on monocytic cells in the presence of 27-hydroxycholesterol (27OHChol). The elevated levels of cytoplasmic membrane HSP60 were verified via Western blot analysis and visualized by confocal microscopy. Treatment with 27OHChol also resulted in increased levels of cellular HSP60 without altering its transcription. Cholesterol, however, did not affect cell-surface levels and cellular amount of HSP60. GSK 2033, an LXR antagonist, inhibited expression of live X receptor α, but not of HSP60, induced by 27OHChol. Treatment with 27OHChol also resulted in increased release of HSP60 from monocytic cells, but the release was significantly reduced by inhibitors of endoplasmic reticulum-Golgi protein trafficking, brefeldin A and monensin. Results of the current study indicate that 27OHChol upregulates not only cell-surface and cellular levels of HSP60 but also its release from monocytic cells, thereby contributing to activation of the immune system.

Diclofenac Inhibits 27-hydroxycholesterol-induced Differentiation of Monocytic Cells into Mature Dendritic Cells

We investigated whether diclofenac could influence the development of antigen-presenting cells in an oxygenated cholesterol-rich environment by determining its effects on the 27-hydroxycholesterol (27OHChol)-induced differentiation of monocytic cells into mature dendritic cells (mDCs). Treatment of human THP-1 monocytic cells with diclofenac antagonized the effects of 27OHChol by attenuating dendrite formation and cell attachment and promoting endocytic function. Diclofenac inhibited the transcription and surface expression of the mDC markers of CD80, CD83, and CD88, and reduced the 27OHChol-induced elevation of surface levels of MHC class I and II molecules to the basal levels in a dose-dependent manner. It also reduced the expression of CD197, a molecule involved in DC homing and migration. These results indicate that diclofenac inhibits the differentiation of monocytic cells into mDCs, thereby potentially modulating adaptive immune responses in a milieu rich in cholesterol oxidation products.

Effect of physical exercise on brain and lipid metabolism in mouse models of multiple sclerosis

Multiple sclerosis (MS) is a central nervous demyelinating disease characterized by cyclic loss and repair of myelin sheaths associated with chronic inflammation and neuronal loss. This degenerative pathology is accompanied by modified levels of oxysterols (oxidative derivatives of cholesterol, implicated in cholesterol metabolism), highlighted in the brain, blood and cerebrospinal fluid of MS patients. The pathological accumulation of such derivatives is thought to participate in the onset and progression of the disease through their implication in inflammation, oxidative stress, demyelination and neurodegeneration. In this context, physical exercise is envisaged as a complementary resource to ameliorate therapeutic strategies. Indeed, physical activity exerts beneficial effects on neuronal plasticity, decreases inflammation and oxidative stress and improves blood-brain integrity in extents that could be beneficial for brain health. The present review attempts to summarize the available data on the positive effect of physical exercise to highlight possible links between physical activity and modulation of cholesterol/oxysterol homeostasis in MS.

PI3K and ERK signaling pathways are involved in differentiation of monocytic cells induced by 27-hydroxycholesterol

27-Hydroxycholesterol induces differentiation of monocytic cells into mature dendritic cells, mDCs. In the current study we sought to determine roles of the PI3K and the ERK pathways in the 27OHChol-induced differentiation. Up-regulation of mDC-specific markers like CD80, CD83 and CD88 induced by stimulation with 27OHChol was significantly reduced in the presence of LY294002, an inhibitor of PI3K, and U0126, an inhibitor of ERK. Surface expression of MHC class I and II molecules elevated by 27OHChol was decreased to basal levels in the presence of the inhibitors. Treatment with LY294002 or U0126 resulted in recovery of endocytic activity which was reduced by 27OHChol. CD197 expression and cell adherence enhanced by 27OHChol were attenuated in the presence of the inhibitors. Transcription and surface expression of CD molecules involved in atherosclerosis such as CD105, CD137 and CD166 were also significantly decreased by treatment with LY294002 and U0126. These results mean that the PI3K and the ERK signaling pathways are necessary for differentiation of monocytic cells into mDCs and involved in over-expression of atherosclerosis-associated molecules in response to 27OHChol.

7α-Hydroxycholesterol induces monocyte/macrophage cell expression of interleukin-8 via C5a receptor

We investigated effects of 7-oxygenated cholesterol derivatives present in atherosclerotic lesions, 7α-hydroxycholesterol (7αOHChol), 7β-hydroxycholesterol (7βOHChol), and 7-ketocholesterol (7K), on IL-8 expression. Transcript levels of IL-8 and secretion of its corresponding gene product by monocytes/macrophages were enhanced by treatment with 7αOHChol and, to a lesser extent, 7K, but not by 7βOHChol. The 7-oxygenated cholesterol derivatives, however, did not change transcription of the IL-8 gene in vascular smooth muscle cells. 7αOHChol-induced IL-8 gene transcription was inhibited by cycloheximide and Akt1 downregulation, but not by OxPAPC. Expression of C5a receptor was upregulated after stimulation with 7αOHChol, but not with 7K and 7βOHChol, and a specific antagonist of C5a receptor inhibited 7αOHChol-induced IL-8 gene expression in a dose dependent manner. Pharmacological inhibitors of PI3K and MEK almost completely inhibited expression of both IL-8 and cell-surface C5a receptor induced by 7αOHChol. These results indicate that 7-oxygenated cholesterol derivatives have differential effects on monocyte/macrophage expression of IL-8 and C5a receptor and that C5a receptor is involved in 7αOHChol-induced IL-8 expression via PI3K and MEK.

Dexamethasone Suppresses Oxysterol-Induced Differentiation of Monocytic Cells

Oxysterol like 27-hydroxycholesterol (27OHChol) has been reported to induce differentiation of monocytic cells into a mature dendritic cell phenotype. We examined whether dexamethasone (Dx) affects 27OHChol-induced differentiation using THP-1 cells. Treatment of monocytic cells with Dx resulted in almost complete inhibition of transcription and surface expression of CD80, CD83, and CD88 induced by 27OHChol. Elevated surface levels of MHC class I and II molecules induced by 27OHChol were reduced to basal levels by treatment with Dx. A decreased endocytosis ability caused by 27OHChol was recovered by Dx. We also examined effects of Dx on expression of CD molecules involved in atherosclerosis. Increased levels of surface protein and transcription of CD105, CD137, and CD166 by treatment with 27OHChol were significantly inhibited by cotreatment with Dx. These results indicate that Dx inhibits 27OHChol-induced differentiation of monocytic cells into a mature dendritic cell phenotype and expression of CD molecules whose levels are associated with atherosclerosis. In addition, we examined phosphorylation of AKT induced by 27OHChol and effect of Dx, where cotreatment with Dx inhibited the phosphorylation of AKT. The current study reports that Dx regulates oxysterol-mediated dendritic cell differentiation of monocytic cells.

Regulation of Adaptive Immunity in Health and Disease by Cholesterol Metabolism

Four decades ago, it was observed that stimulation of T cells induces rapid changes in cellular cholesterol that are required before proliferation can commence. Investigators returning to this phenomenon have finally revealed its molecular underpinnings. Cholesterol trafficking and its dysregulation are now also recognized to strongly influence dendritic cell function, T cell polarization, and antibody responses. In this review, the state of the literature is reviewed on how cholesterol and its trafficking regulate the cells of the adaptive immune response and in vivo disease phenotypes of dysregulated adaptive immunity, including allergy, asthma, and autoimmune disease. Emerging evidence supporting a potential role for statins and other lipid-targeted therapies in the treatment of these diseases is presented. Just as vascular biologists have embraced immunity in the pathogenesis and treatment of atherosclerosis, so should basic and clinical immunologists in allergy, pulmonology, and other disciplines seek to encompass a basic understanding of lipid science.

Oxysterols and symptomatic versus asymptomatic human atherosclerotic plaque

Atherosclerosis is the most common cause of mortality in the Western world, contributing to about 50% of all deaths. Atherosclerosis is characterized by deposition of lipids onto the coronary or carotid arterial wall and formation of an atherosclerotic plaque. Atherosclerotic plaques are categorized into two groups: symptomatic and asymptomatic. The symptomatic plaques tend to be unstable and prone to rupture, and are associated with an increase in ischemic events. Oxysterols, products of cholesterol oxidation, are cytotoxic materials. Their level and type may be associated with plaque formation, development and stability. Oxysterols stimulate the formation of foam cells, advance atherosclerotic plaque progression, and contribute to plaque vulnerability and instability due to their cytotoxicity and their ability to induce cell apoptosis. Studies indicate that plasma 7β-OH CH level can be used as a biomarker for detecting carotid and coronary artery disease. Further clinical studies are needed to evaluate the potential of oxysterols for use as biomarkers for plaque vulnerability and instability. The identification of biomarkers in the blood that can distinguish between symptomatic and asymptomatic plaques remains an unresolved issue.