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Emerging evidence suggests that 7-ketocholesterol (7-KC), one of the most abundant dietary oxysterols, causes inflammation and cardiovascular diseases. Here we show the deteriorating effects of dietary 7-KC on myocardial ischemia–reperfusion (IR) injury and detailed the molecular mechanisms. A high-fat high-cholesterol diet containing 7-KC (7KWD) for 3 weeks increased the plasma 7-KC level compared with high-fat high-cholesterol diet in mice. In wild-type mice but not in CCR2−/− mice, dietary 7-KC increased the myocardial infarct size after IR. Flow cytometry revealed that the ratio of Ly-6Chigh inflammatory monocytes to total monocytes was increased in the 7KWD group. Unbiased RNA sequencing using murine primary macrophages revealed that 7-KC regulated the expression of transcripts related to inflammation and cholesterol biosynthesis. We further validated that in vitro, 7-KC induced endoplasmic reticulum stress, mitochondrial reactive oxygen species production, and nuclear factor-kappa B activation, which are associated with increased mRNA levels of proinflammatory cytokines. Administration of N-acetyl-l-cysteine or siRNA-mediated knockdown of PKR-like endoplasmic reticulum kinase or endoplasmic reticulum oxidase 1α suppressed the levels of 7-KC-induced inflammation. Dietary 7-KC exacerbates myocardial IR injury through monocyte/macrophage-mediated inflammation. Endoplasmic reticulum stress and oxidative stress are involved in the 7-KC-induced proinflammatory response in macrophages.

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Background: Myocardial ischemia-reperfusion (IR) injury limits the beneficial effects of early reperfusion therapy for acute myocardial infarction. Emerging evidence suggests that 7-ketocholesterol (7-KC), one of the most common dietary oxysterols, has pro-inflammatory properties and correlates with cardiovascular diseases. However, the underlying mechanisms remain scant. Here we investigated the effects of 7-KC on myocardial IR injury in mice. Methods and Results: Wild type mice were fed either a control high-fat high-cholesterol diet (HFHCD) or HFHCD containing 7-KC (7KC-HFHCD) for three weeks. In a murine model of 30-min myocardial ischemia and subsequent reperfusion, dietary 7KC-HFHCD increased plasma 7-KC level (145 ± 89.7 ng/mL vs 399 ± 175 ng/mL, P<0.0005, N=8) and infarct size after myocardial IR (52 ± 7.3% vs 64 ± 6.9%, P<0.05, N=8-10) without affecting blood pressure and heart rate. The ratio of Ly-6C high inflammatory monocytes to total monocytes increased in 7KC-HFHCD group as assessed by flow cytometric analysis (49 ± 15% vs 61 ± 9.3%, P<0.05, N=6). We then took a systems approach to explore the pro-inflammatory effects of 7-KC on macrophages and performed unbiased RNA-sequencing using murine peritoneal macrophages stimulated with 7-KC. Pathway analysis of differentially expressed transcripts revealed that 7-KC regulated the expression of transcripts related to inflammation, cholesterol biosynthesis and endoplasmic reticulum (ER) stress. We further validated in vitro that 7-KC induced ER stress, mitochondrial reactive oxygen species, and nuclear factor-kappa B activation associated with increased mRNA levels of pro-inflammatory cytokines such as MCP-1 and TNF-α in murine peritoneal macrophages. Administration of N-acetyl-L-cysteine (5mM), an antioxidant, decreased 7-KC-induced pro-inflammatory cytokines, and this decrease was not observed in Tlr4 -/- murine macrophages, or in macrophages transfected with liver X receptor siRNA. Conclusions: Dietary 7-KC exacerbated myocardial IR injury through macrophage-mediated inflammation in mice. Oxidative stress is involved in the 7-KC-induced pro-inflammatory response in macrophages. Dietary oxysterols are a promising therapeutic target for IR injury.

Background: Emerging evidence suggests that 7-ketocholesterol (7-KC), one of the most abundant dietary oxysterols, causes inflammation and cardiovascular diseases. Here we show the deteriorating effects of dietary 7-KC on myocardial ischemia–reperfusion (IR) injury and detailed the molecular mechanisms.Methods and Results: A high-fat high-cholesterol diet containing 7-KC (7KWD) for 3 weeks increased the plasma 7-KC level compared with high-fat high-cholesterol diet in mice. In wild-type mice but not in CCR2-/- mice, dietary 7-KC increased the myocardial infarct size after IR. Flow cytometry revealed that the ratio of Ly-6Chigh inflammatory monocytes to total monocytes was increased in the 7KWD group. Unbiased RNA sequencing using murine primary macrophages revealed that 7-KC regulated the expression of transcripts related to inflammation and cholesterol biosynthesis. We further validated that in vitro, 7-KC induced endoplasmic reticulum stress, mitochondrial reactive oxygen species production, and nuclear factor-kappa B activation, which are associated with increased mRNA levels of proinflammatory cytokines. Administration of N-acetyl-L-cysteine or siRNA-mediated knockdown of PKR-like endoplasmic reticulum kinase or endoplasmic reticulum oxidase 1α suppressed the levels of 7-KC-induced inflammation.Conclusion: Dietary 7-KC exacerbates myocardial IR injury through monocyte/macrophage-mediated inflammation. Endoplasmic reticulum stress and oxidative stress are involved in the 7-KC-induced proinflammatory response in macrophages.