Thymoquinone Protects against Hyperlipidemia-Induced Cardiac Damage in Low-Density Lipoprotein Receptor-Deficient (LDL-R-/-) Mice via Its Anti-inflammatory and Antipyroptotic Effects

Hyperlipidemia is a risk factor for cardiac damage and cardiovascular disease. Increasing evidence has shown that dyslipidemia-related cardiac damage is associated with lipid accumulation, oxidative stress, and inflammation. Thymoquinone (TQ) is the major constituent of Nigella sativa, commonly known as black seed or black cumin, and is globally used in folk (herbal) medicine for treating and preventing a number of diseases and conditions. Several studies have shown that TQ can protect against cardiac damage. This study is aimed at investigating the possible protective effects of TQ on hyperlipidemia-induced cardiac damage in low-density lipoprotein receptor-deficient (LDL-R-/-) mice. Eight-week-old male LDL-R-/- mice were randomly divided into normal diet (ND), high-fat diet (HFD), and HFD and TQ (HFD+TQ) groups and were fed the different diets for eight weeks. Blood samples were obtained from the inferior vena cava in serum tubes and stored at -80°C until use. Some cardiac tissues were fixed in 10% formalin and then embedded in paraffin for histological evaluation. The remainder of the cardiac tissues was snap-frozen in liquid nitrogen for mRNA preparation or immunoblotting. The levels of metabolism-related factors, such as total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-c), and high-sensitivity C-reactive protein (hs-CRP), were decreased in the HFD+TQ group compared with those in the HFD group. Periodic acid-Schiff staining demonstrated that lipid deposition was lower in the HFD+TQ group than in the HFD group. The expression of pyroptosis indicators (NOD-like receptor 3 (NLRP3), interleukin- (IL-) 1β, IL-18, and caspase-1), proinflammatory factors (IL-6 and tumor necrosis factor alpha (TNF-α)), and macrophage markers (cluster of differentiation (CD) 68) was significantly downregulated in the HFD+TQ group compared with that in the HFD group. Our results indicate that TQ may serve as a potential therapeutic agent for hyperlipidemia-induced cardiac damage.