Shexiang Baoxin Pill for Acute Myocardial Infarction: Clinical Evidence and Molecular Mechanism of Antioxidative Stress

Acute myocardial infarction (AMI) has been a preclinical and clinical concern due to high hospitalization rate and mortality. This study was aimed at evaluating the effectiveness and safety of Shexiang Baoxin Pill (SBP) for AMI and exploring the possible mechanism of oxidative stress. Six databases were searched on March 26, 2021. Twenty-four studies were included and accessed by the RoB 2.0 or SYRCLE tool. Compared with routine treatment (RT), SBP showed the effectiveness in the clinical efficacy (RR = 1.15, 95% CI [1.06, 1.25]), left ventricular ejection fraction (LVEF) (SMD = 0.73, 95% CI [0.62, 0.95]), glutathione (GSH) (SMD = 2.07, 95% CI [1.51, 2.64]), superoxide dismutase (SOD) (SMD = 0.92, 95% CI [0.58, 1.26]), malondialdehyde (MDA) (SMD = −4.23, 95% CI [-5.80, -2.66]), creatine kinase-myocardial band (CK-MB) (SMD = −4.98, 95% CI [-5.64, -4.33]), cardiac troponin I (cTnI) (SMD = −2.17, 95% CI [-2.57, -1.76]), high-sensitivity C-reactive protein (Hs-CRP) (SMD = −1.34, 95% CI [-1.56, -1.12]), interleukin-6 (IL-6) (SMD = −0.99, 95% CI [-1.26, -0.71]), triglycerides (TG) (SMD = −0.52, 95% CI [-0.83, -0.22]), flow-mediated dilation (FMD) (SMD = 1.39, 95% CI [1.06, 1.72]), von Willebrand Factor (vWF) (SMD = −1.77, 95% CI [-2.39, -1.15]), nitric oxide (NO) (SMD = 0.89, 95% CI [0.65, 1.13]), and recurrent rate (RR = 0.30, 95% CI [0.15, 0.59]). But SBP adjunctive to RT plus PCI had no improvements in almost pooled outcomes except for the Hs-CRP (SMD = −1.19, 95% CI [-1.44, -0.94]) and TG (SMD = −0.25, 95% CI [-0.48, -0.02]). Laboratory findings showed that SBP enhanced the endothelial nitric oxide synthase (eNOS) activity and regulated laboratory indexes especially for homocysteine. In conclusion, SBP has adjunctive effects on AMI via the mechanism of antioxidative stress. The current evidence supports the use of SBP for mild and moderate AMI patients.


Introduction
Acute myocardial infarction (AMI) is the sudden damage to the myocardium due to insufficient blood flow to the heart. It is characterized by chest pain, chest discomfort, and acute shortness of breath [1]. Globally, AMI has become the leading cause of hospitalization and death [2]. Early revascularization and primary percutaneous coronary intervention (PCI) restore blood flow to the culprit coronary artery and reduce AMI mortality rate [3,4]. However, immediate mul-tivessel PCI might cause additional risks, e.g., induction of further ischemia, volume overload, and renal impairment due to the use of an increased dose of contrast material [5,6]. Concurrently, the abrupt restoration therapy of coronary flow may induce reversible impairment of myocardial contractility, ventricular arrhythmias, and microvascular dysfunction. The myocardial ischemia/reperfusion (I/R) injury leads to myocyte necrosis, slows cardiomyocyte healing, and results in heart failure [7,8]. Thus, prevention of I/R injury in AMI could reduce the injury.
Shexiang Baoxin Pill (SBP) is a classical Chinese medicine (CM) formula for cardiovascular diseases including AMI and stable angina pectoris [9][10][11], which has been approved by the Chinese Food and Drug Administration [12]. A pharmacological study indicates that SBP reduces cardiac infarct volume, suppresses inflammation, and promotes angiogenesis in the heart [12]. SBP is composed of 7 Chinese medicines or extracts including Moschus, Radix Ginseng, Calculus Bovis, Cortex Cinnamomi, Styrax, Venenum Bufonis, and Borneolum Syntheticum. Ginsenosides and cinnamaldehyde, active components of SBP, regulate energy metabolism in cardiomyocytes [13] and inhibit reactive oxygen species (ROS) production and autophagy [14]. However, the efficacy and mechanisms of SBP for AMI     2.2. Eligibility Criteria. Inclusion criteria were as follows: (1) preclinical experiment (PE) or randomized controlled trial (RCT) studying SPB; (2) animal models of AMI were induced by operation ligation [16,17], or patients met diagnostic criteria for AMI [18][19][20]; (3) SBP was an explored mechanism in preclinical experiments and was used as intervention or adjunctive to routine treatment (RT) in the clinical observation group; and (4) the clinical observation group and control group received RT or PCI. Exclusion criteria were as follows: (1) repetitive studies, comment, clinical experience, case report, review, data mining research, and protocol; (2) non-RCT and PE not studying oxidative stress; (3) PE or RCT contained the intervention of moxibustion, acupuncture, or other CM except for SBP; and (4) the study lacked essential data even though the principal authors were contacted.

Data Extraction.
(1) Basic information of the included experiments (the first author, publication year, animal species, sex, number of animals, weight, intervention, and experiment duration) and trials (the first author, publication year, sample size, age information of the patients, intervention, and trial duration) were extracted; (2) all outcome indicators of experiments were extracted; (3) the primary outcome indicator (clinical efficacy rate) and second outcome indicators (cardiac function, oxidative stress, myocardial enzyme, inflammatory cytokines, blood lipid level, vascular endothelial function, and complication rate) of trials were extracted; and (4) endpoint data and baseline data were extracted for each outcome.

Quality Assessment.
Six aspects of the version 2 of the Cochrane Risk of Bias Tool (RoB 2.0) [21] were assessed for the included RCTs: randomization process, deviations from the intended interventions, missing outcome data, outcome measurements, selection of the reported results, and overall bias according to the three criteria of "low risk," "high risk," or "some concerns." Two researchers (JG and ZQ) assessed the included studies individually, and the third researcher (HC) resolved the discrepancies. GRADE (Grading of Recommendations, Assessment, Development and Evaluations) was used to evaluate evidence certainty of meta-analysis results. The Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) [22] risk of bias tool was used for Pes, including sequence generation, baseline characteristics, allocation concealment, random housing, blinding of performance, random outcome assessment, blinding of detection, incomplete outcome data, selective outcome reporting, and other sources of bias.

Statistical
Analysis. The Stata 17.0 software (Stata Corp., College Station, TX, USA) was applied to statistical analysis: (1) a random effects model was adopted for pooling studies with high heterogeneity while a fixed effects model was applied for studies with low heterogeneity; (2) Cohen's d and 95% CI were used for continuous variables; (3) RR (relative risk) and 95% CI were used for categorical variables; (4) weight (%) was used to indicate a percentage of each study contributing to the pooled intervention effects; (5) a p value < 0.05 was considered statistically different; (6) heterogeneity was evaluated by Q statistics and I 2 , and the p value in Q statistics was <0.05 or I 2 > 50% presented high heterogeneity or otherwise low heterogeneity; and (7) sensitivity analysis and subgroup analysis were carried out when studies had significant heterogeneity.

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Oxidative Medicine and Cellular Longevity

Discussion
This review explored the clinical evidence of SBP for AMI in RCTs and antioxidant effects of SBP for AMI in PEs, respectively. In the PEs, we found that SBP enhanced the eNOS activity during oxidative stress and regulated several laboratory indexes involving oxidative damage, including hippuric acid, homocysteine, 5-methylcytosine, PGPC, allan-toin indoleacrylic acid, 6-hydroxymelatonin, and thymidine. From the pooled analysis of RCTs, SBP plus RT showed significantly improved clinical efficacy rate, cardiac function, and vascular endothelial function and reduced myocardial enzyme, inflammatory cytokines, blood lipid level, and complication rate. Hence, SBP not only showed the benefits for AMI in RCT but also had antioxidative effects in AMI animal models. Notably, the adjunctive effects of SBP adjunctive to RT plus PCI were diminished in most outcomes except for Hs-CRP and TG levels. It may be attributed to the ceiling effect of PCI for AMI treatment.
Oxidative stress plays a major role in cardiovascular diseases [47][48][49]. Combined with our preclinical review, SBP removes superoxide anion (O •− 2 ) through several antioxidative stress mechanisms (Figure 7). SBP protects against endothelial cell injury by activating eNOS activity and promoting nitric oxide (NO) production [50,51]  lead to oxidative damage of endothelial cells [58]. Several active components of SBP have been identified. Cinnamaldehyde decreases the O •− 2 generation through the toll-like receptor 4-NADPH oxidase 4 (TLR4-NOX4) pathway in the lipopolysaccharide-induced cardiac dysfunction [14]. Ginsenoside Rc, one component of SBP, activates a histone deacetylase, sirtuin type 1 (SIRT1), and suppresses ROS [13,59]. The collecting evidence indicates that SBP has antioxidant effects on AMI. As SBP consists of multiple Chinese medicines, the antioxidant effects could involve multiple active components and multiple mechanisms. A few questions have not been fully addressed; e.g., how many active components are in SBP? What are the mechanisms of these active components suppressing ROS?
This systematic review and meta-analysis included RCTs to evaluate the clinical effects of SBP following the PRISMA guideline. Nevertheless, the overall quality of included RCTs is poor according to the risk of bias assessment, and half of the pooled analysis involving PCI showed high heterogeneity. Compared with RT plus PCI, we found that the SBP adjunctive to RT plus PCI does not significantly affect the AMI recurrence rate and even decreases the LVEF level in one study [40]. Given the inadequate inclusion of RCTs involving PCI, the study cannot confirm the effectiveness of SBP adjunctive to RT plus PCI even though it significantly improves the Hs-CRP and TG levels. Hence, our findings suggest that SBP can be recommended for patients with mild or moderate AMI rather than severe AMI patients requiring PCI treatment. Whether SBP benefits patients with severe AMI needs to be evaluated by rigorous RCTs further.

Conclusions
SBP protects against oxidative stress in AMI via multiple mechanisms. Clinical evidence indicates that SBP adjunctive to RT improves the clinical efficacy rate, cardiac function, and other clinical indexes of AMI. The current evidence supports the use of SBP for mild and moderate AMI patients.

Disclosure
The funders were not involved in the collection, management, analysis, and interpretation of data.