目的: 研究超细颗粒物(ultrafine particulates,UFPs)对大鼠离体心脏功能的影响及其机制。方法: 以含或不含UFPs的台式液经Langendorff系统持续灌流大鼠离体心脏模型40 min,观察灌流前后两组大鼠心脏血流动力学指标[左心室舒张压(left ventricular developed pressure,LVDP)、左心室内压最大上升和最大下降速率(±dp/dt_max)及冠脉流量(coronary flow,CF)]的变化。收集肺动脉流出液,采用硫代巴比妥酸法测定丙二醛(malondialdehyde,MDA),水溶性四唑盐法测定超氧化物歧化酶(superoxide dismutase,SOD), 比色法测定总抗氧化能力(total antioxidant capacity,TAOC)。免疫组织化学法和Western blots法测定两组心脏标本p-p38 MAPK、p-JNKs、p-ERKs的表达。结果: 相对于对照组,UFPs灌流组大鼠离体心脏功能指标LVDP、+dp/dt_max、-dp/dt_max、CF分别从(82.6 ± 2.1) mmHg、(1 624 ± 113) mmHg/s、(1 565 ± 116) mmHg/s、(12.0 ± 0.2) mL/min降至灌注结束时的(56.8 ± 4.4) mmHg、(1 066 ± 177) mmHg/s、(1 082 ± 134) mmHg/s、(8.7 ± 0.3) mL/min,各指标灌流结束时相比灌流初始值差异均有统计学意义(P<0.05)。UFPs灌流组肺动脉流出液MDA含量明显高于对照组[(1.95±0.18) nmol/L vs. (0.98±0.14) nmol/L,P<0.05],而SOD、TAOC明显低于对照组[(6.50±1.04) U/mL vs. (12.50±1.87) U/mL,(3.67±0.82) U/mL vs. (6.83±1.16) U/mL, P<0.05 ]。UFPs灌流组p-p38 MAPK、p-JNKs、p-ERKs 较对照组表达明显增加(P<0.05)。结论: UFPs短期暴露对大鼠离体心脏有直接的急性毒性作用,其作用机制可能与氧化应激及MAPK信号通路激活有关。

Objective: To evaluate whether ultrafine particulates (UFPs) have direct deleterious effects on cardiac function through activating MAPK signaling. Methods: Langendorff-perfused Sprague-Dawley rat hearts were randomly divided into 2 groups (n=10/each group). In control group, the rat hearts were perfused with Tyrode’s buffer for 40 min; in UFPs-treated group, the hearts were perfused with UFPs at a concentration of 12.5 mg/L. Cardiac function was determined by measuring left ventricular developed pressure (LVDP), left ventricular peak rate of contraction and relaxation (±dp/dt_max) and coronary flow (CF). The levels of malondialdehyde (MDA), superoxide dismutase (SOD), total anti-oxidant capacity (TAOC) were detected in order to evaluate cardiac oxidative stress via the thiobarbituric acid assay, water soluble tetrazolium salt assay and colorimetry, respectively. The expressions of p-p38 MAPK, p-ERKs and p-JNKs in the myocardium were observed using immunohistochemical staining and Western blots. Results: No significant changes in cardiac function were detected before and after the perfusion in control group while UFPs perfused hearts showed a decline in cardiac function in a time-dependent manner (all P<0.05). In UFPs-treated group, LVDP, +dp/dt_max, -dp/dt_max and CF were statistically reduced from (82.6±2.1) mmHg, (1 624±113) mmHg/s, (1 565±116) mmHg/s, (12.0±0.2) mL/min to (56.8±4.4) mmHg, (1 066±177) mmHg/s, (1 082±134) mmHg/s, (8.7±0.3) mL/min (all P<0.05), respectively. Furthermore, The comparison between the two groups observed that UFPs perfusion caused a significant decrease in cardiac function at 30 and 40 min compared with the control group (all P<0.05). At the end of the perfusion, the level of MDA was increased from (0.98±0.14) nmol/L to (1.95±0.18) nmol/L, while SOD and TAOC were reduced from (12.50±1.87) U/mL and (6.83±1.16) U/mL to (6.50 ±1.04) U/mL and (3.67±0.82) U/mL (all P<0.001) in UFPs group, respectively. In coincidence with these changes, immunohistochemistry and Western blots results showed that the levels of p-p38 MAPK, p-ERKs and p-JNKs in the myocardium significantly increased in UFPs group as compared with control group (all P<0.05). Conclusion: The results of this study demonstrated that the short-term exposure of UFPs to the isolated rat hearts has direct and acute toxic effects on cardiac function, probably related to attenuation of anti-oxidative capacity and activation of MAPK signaling pathways.