Titanium dioxide nanoparticles (TiO2 NPs) are widely used in food and cosmetics but the health impact of human exposure remains poorly defined. Emerging evidence suggests that TiO2 NPs may elicit immune responses by acting on macrophages. Our proteomic study showed that treatment of macrophages with TiO2 NPs led to significant re-organization of cell membrane and activation of inflammation. These observations were further corroborated with transmission electron microscopy (TEM) experiments, which demonstrated that TiO2 NPs were trapped inside of multi-vesicular bodies (MVB) through endocytotic pathways. TiO2 NP caused significant mitochondrial dysfunction by increasing levels of mitochondrial reactive oxygen species (ROS), decreasing ATP generation, and decreasing metabolic flux in tricarboxylic acid (TCA) cycle from 13C-labelled glutamine using GC-MS-based metabolic flux analysis. Further lipidomic analysis showed that TiO2 NPs significantly decreased levels of cardiolipins, an important class of mitochondrial phospholipids for maintaining proper function of electron transport chains. Furthermore, TiO2 NP exposure activates inflammatory responses by increasing mRNA levels of TNF-α, iNOS, and COX-2. Consistently, our targeted metabolomic analysis showed significantly increased production of COX-2 metabolites including PGD2, PGE2, and 15d-PGJ2. In addition, TiO2 NP also caused significant attenuation of phagocytotic function of macrophages. In summary, our studies utilizing multiple powerful omic techniques suggest that human exposure of TiO2 NPs may have profound impact on macrophage function through activating inflammatory responses and causing mitochondrial dysfunction without physical presence in mitochondria.

Coronary heart disease (CHD) is a complex human disease associated with inflammation and oxidative stress. The underlying mechanisms and diagnostic biomarkers for the different types of CHD remain poorly defined. Metabolomics has been increasingly recognized as an enabling technique with the potential to identify key metabolomic features in an attempt to understand the pathophysiology and differentiate different stages of CHD. We performed comprehensive metabolomic analysis in human plasma from 28 human subjects with stable angina (SA), myocardial infarction (MI), and healthy control (HC). Subsequent analysis demonstrated a uniquely altered metabolic profile in these CHD: a total of 18, 37 and 36 differential metabolites were identified to distinguish SA from HC, MI from SA, and MI from HC groups respectively. Among these metabolites, glycerophospholipid (GPL) metabolism emerged as the most significantly disturbed pathway. Next, we used a targeted metabolomic approach to systematically analyze GPL, oxidized phospholipid (oxPL), and downstream metabolites derived from polyunsaturated fatty acids (PUFAs), such as arachidonic acid and linoleic acid. Surprisingly, lipids associated with lipid peroxidation (LPO) pathways including oxidized PL and isoprostanes, isomers of prostaglandins, were significantly elevated in plasma of MI patients comparing to HC and SA, consistent with the notion that oxidative stress-induced LPO is a prominent feature in CHD. Our studies using the state-of-the-art metabolomics help to understand the underlying biological mechanisms involved in the pathogenesis of CHD; LPO metabolites may serve as potential biomarkers to differentiation MI from SA and HC.

We found serum lipid profiles changed in women with PCOS. Obesity and compensatory hyperinsulinemia promoted the metabolism of arachidonic acid and other PUFAs, whereas androgen had an inhibitory effect.

Oxidative stress and inflammation are two major contributing factors to atherosclerosis, a leading cause of cardiovascular disease. Oxidation of phospholipids on the surface of low density lipoprotein (LDL) particles generated under oxidative stress has been associated with the progression of atherosclerosis, but the underlying molecular mechanisms remain poorly defined. We identified a novel series of oxidation products containing the cyclopentenone moiety, termed deoxy-A/J-isoprostanes-phosphocholine, from 1-palmitoyl-2-arachidonoyl--glycero-3-phosphocholine using mass spectrometry and by comparison to a chemically synthesized standard. Transcriptomic analysis (RNA-seq) demonstrated that these compounds affected>200 genes in bone marrow-derived macrophages, and genes associated with inflammatory and anti-oxidative responses are among the top 5 differentially expressed. To further investigate the biological relevance of these novel oxidized phospholipids in atherosclerosis, we chemically synthesized a representative compound 1-palmitoyl-2-15-deoxy-δ-12,14-prostaglandin J--glycero-3-phosphocholine (15d-PGJ-PC) and found that it induced anti-inflammatory and anti-oxidant responses in macrophages through modulation of NF-κB, peroxisome proliferator-activated receptor γ (PPARγ), and Nrf2 pathways; this compound also showed potent anti-inflammatory properties in a mice model of LPS-induced systematic inflammatory response syndrome. Additionally, 15d-PGJ-PC inhibited macrophage foam cell formation, suggesting a beneficial role against atherosclerosis. These properties were consistent with decreased levels of these compounds in the plasma of patients with coronary heart disease compared with control subjects. Our findings uncovered a novel molecular mechanism for the negative regulation of inflammation and positive enhancement of anti-oxidative responses in macrophages by these oxidized phospholipids in LDL in the context of atherosclerosis.

Dysregulation of cholesterol metabolism represents one of the major risk factors for atherosclerotic cardiovascular disease (CVD). Oxidized cholesterol esters (oxCE) in low-density lipoprotein (LDL) have been implicated in CVD but the underlying mechanisms remain poorly defined. We use a targeted lipidomic approach to demonstrate that levels of oxCEs in human plasma are associated with different types of CVD and significantly elevated in patients with myocardial infarction. We synthesized a major endogenous cholesterol ester hydroperoxide (CEOOH), cholesteryl-13(cis, trans)-hydroperoxy-octadecadienoate (ch-13(c,t)-HpODE) and show that this endogenous compound significantly increases plasma cholesterol level in mice while decrease cholesterol levels in mouse liver and peritoneal macrophages, which is primarily due to the inhibition of cholesterol uptake in macrophages and liver. Further studies indicate that inhibition of cholesterol uptake by ch-13(c,t)-HpODE in macrophages is dependent on LXRα-IDOL-LDLR pathway, whereas inhibition on cholesterol levels in hepatocytes is dependent on LXRα and LDLR. Consistently, these effects on cholesterol levels by ch-13(c,t)-HpODE are diminished in LDLR or LXRα knockout mice. Together, our study provides evidence that elevated plasma cholesterol levels by CEOOHs are primarily due to the inhibition of cholesterol uptake in the liver and macrophages, which may play an important role in the pathogenesis of CVD.

No abstract

The metabolism of polyunsaturated fatty acids (PUFAs) remains poorly characterized in ovarian tissues of patients with polycystic ovary syndrome (PCOS). This study aimed to explore alterations in the levels of PUFAs and their metabolites in serum and ovarian tissues in a PCOS rat model treated with a high‐fat diet and andronate. Levels of PUFAs and their metabolites were measured using gas/liquid chromatography‐mass spectrometry after the establishment of a PCOS rat model. Only 3 kinds of PUFAs [linoleic acid, arachidonic acid (AA) and docosahexaenoic acid] were detected in both the circulation and ovarian tissues of the rats, and their concentrations were lower in ovarian tissues than in serum. Moreover, significant differences in the ovarian levels of AA were observed between control, high‐fat diet‐fed and PCOS rats. The levels of prostaglandins, AA metabolites via the cyclooxygenase (COX) pathway, in ovarian tissues of the PCOS group were significantly increased compared to those in the controls. Further studies on the mechanism underlying this phenomenon showed a correlation between decreased expression of phosphorylated cytosolic phospholipase A2 (p‐cPLA2) and increased mRNA and protein expression of COX2, potentially leading to a deeper understanding of altered AA and prostaglandin levels in ovarian tissues of PCOS rats.

Polycystic ovary syndrome (PCOS) is a heterogeneous disease characterized by various endocrine/metabolic disorders and impaired reproductive potential. Alterations in oocyte competence are considered potentially causative factor for infertility in PCOS women and analyzing the composition of follicular fluid in these patients may help to identify which changes have the potential to alter oocyte quality. In this study, free fatty acid metabolic signatures in follicular fluid were performed to identify changes that may impact oocyte competence in non-obese PCOS women. Sixty-four non-obese women (32 with PCOS and 32 age- and BMI-matched controls) undergoing in vitro fertilization were recruited. Embryo quality was morphologically assessed. Free fatty acid metabolic profiling in follicular fluid was performed using gas/liquid chromatography-mass spectrometry. Principal component analysis and orthogonal partial least squares-discriminant analysis models were further constructed. Nine free fatty acids and twenty-four eicosanoids were identified and several eicosanoids synthesized by the cyclooxygenase pathway were significantly elevated in PCOS patients compared to controls. The combination of PGE2, PGF2α, PGJ2, and TXB2 had an area under the curve of 0.867 (0.775–0.960) for PCOS discrimination. Furthermore, follicular fluid levels of PGE2 and PGJ2 were negatively correlated with high-quality embryo rate in PCOS patients (P < 0.05). Metabolomic analysis revealed that follicular fluid lipidomic profiles undergo changes in non-obese PCOS women, which suggest that identifying changes in important metabolic signatures may give us a better understanding of the pathogenesis of PCOS. Furthermore, elevated PGE2 and PGJ2 concentrations may contribute to impaired oocyte competence in non-obese PCOS patients.