Background Long-term exposure to ambient fine particulate matter (PM_2.5) is a significant risk factor for cardiometabolic disorders. However, the mechanisms of its interaction with the endogenous circadian system remain incompletely understood. Objective To investigate whether chronic PM_2.5 exposure interferes with the rhythmic expression of the cardiac circadian clock, thereby disrupting downstream antioxidant defenses and metabolic homeostasis, and ultimately driving cardiometabolic dysfunction. Methods Seventy-two male C57BL/6 mice were randomly divided into a PM_2.5 exposure group (PM group) and a filtered air control group (FA group). Whole-body exposure was conducted for 8 weeks in a meteorological environmental animal exposure system. Samples were collected at six distinct zeitgeber time (ZT) points post-exposure. The 24 h ambulatory blood pressure and serum lipid profiles were monitored. Rhythm parameters were derived via cosinor analysis to compare differences in Midline statistic of rhythm (Mesor), amplitude, and phase between the two groups. The rhythmic expression of core circadian clock genes and antioxidant genes in the myocardium was detected by quantitative polymerase chain reaction (qPCR). Myocardial reactive oxygen species (ROS) levels and downstream pathway protein expression were analyzed by immunofluorescence and Western blot (WB), respectively. The expression changes of the clock gene retinoic acid receptor-related orphan receptor α (RORα) were assessed at both the mRNA and protein levels. Finally, Spearman correlation analysis was used to explore the relationships among myocardial RORα expression, lipid profiles, and oxidative stress indicators. Results Compared to the FA group, mice in the PM group exhibited a blunted circadian rhythm in blood pressure, characterized by sustained elevation throughout the day. Chronic PM_2.5 exposure showed a significant interaction with ZT on systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) (F-interaction=9.11, 5.70, and 6.02, respectively; P<0.05), as well as on serum triglycerides (TG), total cholesterol (T-CHO), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) (F-interaction=16.32, 11.12, 15.39, and 28.09, respectively; P<0.05). Cosinor analysis further revealed that the Mesor values of T-CHO, TG, and LDL-C were significantly increased (P<0.05), while that of HDL-C was significantly decreased in the PM group (P<0.05). The oscillation amplitudes of SBP, DBP, and MAP showed a decreasing trend, whereas those of TG and LDL-C were significantly increased (P<0.05). Furthermore, SBP, T-CHO, and HDL-C all exhibited a significant phase delay (P<0.05). Mechanistically, PM_2.5 exposure significantly suppressed the expression of the positive circadian regulator RORα in the myocardium, leading to disordered rhythmic expression of core clock genes (Bmal1, Clock, Per1/2, and Cry1/2). This exposure also inhibited the rhythmic expression of antioxidant genes (GPX1, SOD2, and CAT), resulting in increased ROS generation and elevated expression of calcium/calmodulin-dependent protein kinase II (CaMKII) and reduced nicotinamide adenine dinucleotide phosphate (NADPH) proteins. Correlation analysis further revealed that myocardial RORα expression level was negatively correlated with T-CHO, TG, and LDL-C (r=−0.55, −0.63, and −0.51, respectively; P<0.001), and positively correlated with HDL-C (r=0.37, P=0.010), and antioxidant genes GPX1, SOD2, and CAT expression (r=0.34, 0.35, and 0.56, respectively; P < 0.001). Conclusion Chronic PM_2.5 exposure induces cardiometabolic dysfunction by suppressing myocardial RORα expression. This suppression disrupts the cardiac circadian clock and the diurnal balance of oxidative stress, triggering oxidative damage and elevating expression of CaMKII/NADPH pathway proteins. Collectively, these alterations precipitate the loss of cardiac metabolic rhythms and subsequent functional impairment.

Background Ozone (O₃) pollution has gradually become a primary problem of air pollution in recent years. Conducting epidemiological studies on the correlation between O₃ concentration variation and risk of cardiovascular and cerebrovascular diseases can provide reference data for O₃ risk assessment and related policy making. Objective To quantitatively evaluate the effects of O₃ exposure on mortalities of cardiovascular and cerebrovascular diseases among residents in Minhang District, Shanghai. Methods Data of mortalities of cardiovascular and cerebrovascular diseases, air pollutants, and meteorological factors in Minhang District of Shanghai from January 1, 2016 to December 31, 2021 were collected. Associations between O₃ concentration and the mortalities due to total cardiovascular and cerebrovascular diseases, coronary heart disease, and stroke were analyzed by generalized additive models with a quasi Poisson distribution with different lag patterns, such as current day effect (lag0), single-day lag effects (lag1-lag3), and cumulative lag effects (lag01-lag03). The subgroup analyses of age, sex, and season were conducted. Furthermore, temperature was divided into low, middle, and high levels based on the 25th percentile (P₂₅) and the 75th percentile (P₇₅) to perform hierarchical analyses. Increased excess risks (ER) of death from target diseases caused by a 10 µg·m⁻³ increase in daily maximum 8 h concentration of O₃ (O₃-8 h) and their 95% confidence intervals (CI) were used to indicate the effects of O₃. Results The associations between O₃ and the risks of death from cardiovascular and cerebrovascular diseases were statistically significant at lag2, lag3, lag02, and lag03 (P<0.05), with the greatest effect size observed at lag03. The ER values of death from cardiovascular and cerebrovascular diseases in general population, male residents, and people aged 65 years and older, from coronary heart disease in male residents, and from stroke in general population increased by 1.02% (95%CI: 0.36%, 1.69%), 1.40% (95%CI: 0.47%, 2.34%), 0.87% (95%CI: 0.19%, 1.55%), 1.96% (95%CI: 0.49%, 3.44%), and 1.02% (95%CI: 0.07%, 1.98%) for a 10 µg·m⁻³ increase in O₃-8 h concentration at lag03, respectively. During the warm season (from April 1 to September 30), the ER values of death from cardiovascular and cerebrovascular diseases and coronary heart disease per 10 µg·m⁻³ increase in O₃ were 1.18% (95%CI: 0.33%, 3.33%) and 2.69% (95%CI: 0.39%, 5.03%), while the O₃ effect was only statistically significant on cardiovascular and cerebrovascular diseases during the cold season (from October 1 to March 31 next year). At the middle and high temperature levels, the ER values of death from cardiovascular and cerebrovascular diseases increased by 1.63% (95%CI: 0.32%, 2.96%) and 1.14% (95%CI: 0.17%, 2.12%) respectively. The two-pollutant models showed similar results after including other pollutants (carbon monoxide, nitrogen dioxide, sulfur dioxide, fine particulate matter, or inhalable particulate matter). Conclusion Ambient O₃ pollution may increase the mortality risks of cardiovascular and cerebrovascular diseases, coronary heart disease, and stroke in Minhang District of Shanghai.