Identification of Transcription Factor-Gene Regulatory Network in Acute Myocardial Infarction.

BACKGROUND: Acute myocardial infarction (AMI) is a common disease with serious mortality and morbidity, worldwide. The present study aimed to identify differentially expressed genes (DEGs) and construct a transcription factor-gene regulatory network to further study the early diagnosis of AMI. METHODS: The integrated analysis of publicly available Gene Expression Omnibus datasets of AMI was performed. Differentially expressed genes were identified between AMI and normal blood samples. Gene Ontology enrichment analyses, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, and the transcription factor-gene regulatory network were used to obtain insights into the functions of DEGs. Quantitative real-time polymerase chain reactions (qRT-PCR) were performed to validate the expression level of DEGs. RESULTS: A total of 2,502 DEGs, including 917 up-regulated genes and 1,585 down-regulated genes, were identified between AMI and normal blood samples by integrating four expression profiles of AMI. Differentially expressed genes were significantly enriched in pathways including complement and coagulation cascades, Staphylococcus aureus infection, and cell adhesion molecules. Transcription factors were screened and performed to construct the regulatory network. The transcription factor-gene regulatory network consisted of 871 interactions between 80 transcription factors and 716 DEGs. ETS homologous factor (EHF) was one of transcription factors that had high connectivity with DEGs and regulated CACNB4 in the network. Verification by qRT-PCR revealed that EHF, KRT6A and DSG3 were significantly up-regulated, while CACNG4 was significantly down-regulated in AMI. Furthermore, CACNG6, CACNB4 and CLDN18 had a tendency to be down-regulated, and CALML3 had a tendency to be up-regulated in AMI. CONCLUSIONS: The identification of important differentially expressed transcription factors and genes in the development of AMI would be the groundwork for the early diagnosis and early intervention of AMI.

Overexpression of VEGF-C attenuates chronic high salt intake-induced left ventricular maladaptive remodeling in spontaneously hypertensive rats.

Recent studies have shown that the tonicity-responsive enhancer binding protein (TonEBP)/vascular endothelial growth factor-C (VEGF-C) signaling pathway-induced lymphangiogenesis provides a buffering mechanism for high salt (HS) intake-induced elevation of blood pressure (BP). Moreover, blocking of TonEBP/VEGF-C signaling by mononuclear phagocyte depletion can induce salt-sensitive hypertension in rats. We hypothesized that HS intake could have an impact on cardiac lymphangiogenesis, and regulation of VEGF-C bioactivity, which is largely through the main receptor for VEGFR-3, may modulate HS intake-induced left ventricular remodeling. We demonstrated upregulation of TonEBP, increased macrophage infiltration, and enhanced lymphangiogenesis in the left ventricles of spontaneously hypertensive rats (SHR) that were fed a HS diet (8.0% NaCl). Then, retrovirus vectors capable of overexpression (ΔNΔC/VEGF-C/Cys152Ser, used for overexpressing VEGF-C) and blocking (VEGFR-3-Rg, used for trapping of bioactive VEGF-C) of VEGF-C and control vector (pLPCX) were intravenously administered to SHR from week 9 of a 12-wk HS loading period. At the end of the HS challenge, overexpression of VEGF-C led to enhanced cardiac lymphangiogenesis, decreased myocardial fibrosis, and macrophage infiltration, preserved left ventricular functions, as well as decreased blood pressure level compared with the HS group and the control vector-treated HS group. In contrast, systemic blocking of VEGF-C was associated with elevation of blood pressure level and an exacerbation of hypertensive left ventricular remodeling, as indicated by increased fibrosis and macrophage infiltration, and diminished lymphangiogenesis. Hence, our findings highlight that VEGF-C/VEGFR-3 is a promising therapeutic target to attenuate hypertensive left ventricular remodeling induced by HS intake, presumably via blood pressure-dependent and -independent mechanisms.

Monocyte subsets and monocyte-platelet aggregates in patients with unstable angina.

Monocyte subsets and monocyte-platelet aggregates (MPAs) play important role in atherosclerosis and thrombosis. We aimed to determine their changes in patients with unstable angina (UA). In this cross-sectional case-control study, Global Registry of Acute Coronary Events (GRACE) score was determined in 95 UA patients without elevated troponin level. Thirty age-and-sex matched stable coronary heart disease (CHD) subjects served as control group. The classical (CD14++CD16-, Mon1), the intermediate (CD14++CD16+, Mon2) and the non-classical (CD14+CD16++, Mon3) monocytes, as well as subset-specific MPAs, were measured by flow cytometry. Compared with stable CHD patients, UA patients had increased Mon2 and Mon3 counts (all P < 0.001). For UA subjects, compared with GRACE score-determined low risk patients (GRACE score ≤108, n = 70), intermediate-to-high risk patients (GRACE score >108, n = 25) had higher counts of Mon2 and total MPAs, as well as Mon1- and Mon2-associated MPAs (all P < 0.001). Adjusted binary logistic regression analysis revealed that increased counts of Mon2 subset (for per 5 cells/µL increase, OR 1.186, 95% CI 1.044-1.347, P = 0.009), Mon2 MPAs (for per 5 cells/µL increase, OR 1.228, 95% CI 1.062-1.421, P = 0.006) and total MPAs (for per 5 cells/µL increase, OR 1.072, 95 % CI 1.010-1.137, P = 0.022) independently associated with GRACE score-determined intermediate-to-high risk UA patients. In UA patients with intermediate-to-high risk (determined by GRACE score), counts of Mon2 subset, Mon2-associated MPAs and total MPAs are increased, which are independent of traditional risk factors.

Chronic high­salt intake induces cardiomyocyte autophagic vacuolization during left ventricular maladaptive remodeling in spontaneously hypertensive rats.

The role of autophagy in high-salt (HS) intake associated hypertensive left ventricular (LV) remodeling remains unclear. The present study investigated the LV autophagic change and its association with the hypertensive LV remodeling induced by chronic HS intake in spontaneously hypertensive rats (SHR). Wistar Kyoto (WKY) rats and SHR were fed low-salt (LS; 0.5% NaCl) and HS (8.0% NaCl) diets and were subjected to invasive LV hemodynamic analysis after 8, 12 and 16 weeks of dietary intervention. Reverse transcription-quantitative PCR and western blot analysis were performed to investigate the expression of autophagy-associated key components. The LV morphologic staining was performed at the end of the study. The rat H9c2 ventricular myoblast cell-associated experiments were performed to explore the mechanism of HS induced autophagic change. A global autophagy-associated key component, as well as increased cardiomyocyte autophagic vacuolization, was observed after 12 weeks of HS intake. During this period, the heart from HS-diet-fed SHR exhibited a transition from compensated LV hypertrophy to decompensation, as shown by progressive impairment of LV function and interstitial fibrosis. Myocardial extracellular [Na+] and the expression of tonicity-responsive enhancer binding protein (TonEBP) was significantly increased in HS-fed rats, indicating myocardial interstitial hypertonicity by chronic HS intake. The global autophagic change and overt deterioration of LV function were not observed in LS-fed SHR and HS-fed WKY rats. The study of rat H9c2 cardiomyocytes demonstrated a cytosolic [Na+] elevation-mediated, reactive oxygen species-dependent the autophagic change occurred when exposed to an increased extracellular [Na+]. The present findings demonstrated that a myocardial autophagic change participates in the maladaptive LV remodeling induced by chronic HS intake in SHR, which provides a possible target for future intervention studies on HS-induced hypertensive LV remodeling.

Correlation between angiopoietin-like proteins in inflammatory mediators in peripheral blood and severity of coronary arterial lesion in patients with acute myocardial infarction.

The effects of angiopoietin-like protein 2 (Angptl 2) and interleukin-6 (IL-6) in inflammatory mediators on the severity of coronary arterial lesion in patients with acute myocardial infarction were investigated. One hundred and twenty-six patients with acute myocardial infarction admitted to Tianjin Union Medical Center (the myocardial infarction group) and 133 healthy individuals (the control group) were selected for retrospective analysis from January 2013 to December 2015. The levels of Angptl 2 and IL-6 in serum of patients were detected by enzyme linked immunosorbent assay (ELISA), and the correlation analysis between the levels and the degree of coronary stenosis in patients with myocardial infarction was conducted. The expression level of Angptl 2 and IL-6 in the myocardial infarction group was significantly higher than that in the control group P<0.001. In the myocardial infarction group, the expression levels of Angptl 2 and IL-6 were the highest in the patients with severe stenosis, followed by the moderate stenosis, and the lowest in the patients with mild stenosis (P<0.050). Pearson's correlation analysis showed that Angptl 2 and IL-6 were positively correlated with the diameter of coronary stenosis (r=0.696, 0.750, P<0.001). In conclusion, both Angptl 2 and IL-6 are highly expressed in the peripheral blood of patients with acute myocardial infarction and involved in the occurrence and development of the disease. Moreover, Angptl2 and IL-6 are positively correlated with the severity of coronary arterial lesion in patients with acute myocardial infarction, and they are expected to become a target for the diagnosis and treatment of coronary atherosclerosis (CA) in the future.

Voltage-gated sodium channel inhibitor reduces atherosclerosis by modulating monocyte/macrophage subsets and suppressing macrophage proliferation.

Inflammatory monocyte and macrophage subset accumulation during the inflammatory response that drives atherosclerosis can exacerbate the extent of atherosclerosis. It has been demonstrated that voltage-gated sodium channels (VGSCs) can regulate cell bioactivities in monocytes/macrophages. We hypothesized that blockade of mononuclear phagocyte VGSCs was atheroprotective through monocyte/macrophage subset modulation and macrophage proliferation suppression in atherosclerotic lesions. In this experimental study, when VGSCs were knocked down with RNA interference plasmid transfection in mouse peripheral blood monocytes and monocyte-macrophage lineage RAW264.7 cells in vitro, the biological characteristics of proliferation, phagocytosis, and migration in RAW264.7 cells declined. In addition, suppression of LPS-induced M1 polarization and facilitation of IL-4-induced M2 polarization were also observed. In an in vivo study, ApoE knockout (ApoE-/-) mice were fed a standard chow diet (CD) or a western diet (WD). After feeding with phenytoin (PHT), no significant differences were detected in plasma lipids, and the anti-inflammatory phenotypes of both monocytes and macrophages were elevated and proinflammatory phenotypes declined. The local proliferation of macrophages was also distinctly suppressed, along with a significant reduction in atheromatous plaques. In conclusion, blockade of VGSCs in the mononuclear phagocyte system reduced atherosclerotic lesions, which may occur through altering monocyte/macrophage subsets and suppressing macrophage proliferation in atherosclerotic plaques. Blockage of VGSCs may play an important role in cardiovascular protection.

Trajectories of Circulating Monocyte Subsets After ST-Elevation Myocardial Infarction During Hospitalization: Latent Class Growth Modeling for High-Risk Patient Identification.

It remains unclear if the developmental trajectories of a specific inflammatory biomarker during the acute phase of ST-elevation myocardial infarction (STEMI) provide outcome prediction. By applying latent class growth modeling (LCGM), we identified three distinctive trajectories of CD14++CD16+ monocytes using serial flow cytometry assays from day 1 to day 7 of symptom onset in 96 de novo STEMI patients underwent primary percutaneous coronary intervention. Membership in the high-hump-shaped trajectory (16.8%) independently predicted adverse cardiovascular outcomes during a median follow-up of 2.5 years. Moreover, inclusion of CD14++CD16+ monocyte trajectories significantly improved area under the curve (AUC) when added to left ventricular ejection fraction-based prediction model (ΔAUC = 0.093, P = 0.013). Therefore, CD14++CD16+ monocyte trajectories during STEMI hospitalization are a novel risk factor for post-STEMI adverse outcomes. These results provide the first proof-of-principle evidence in support of the risk stratification role of LCGM-based longitudinal modeling of specific inflammatory markers during acute STEMI.

Gut-dependent microbial translocation induces inflammation and cardiovascular events after ST-elevation myocardial infarction.

BACKGROUND: Post-infarction cardiovascular remodeling and heart failure are the leading cause of myocardial infarction (MI)-driven death during the past decades. Experimental observations have involved intestinal microbiota in the susceptibility to MI in mice; however, in humans, identifying whether translocation of gut bacteria to systemic circulation contributes to cardiovascular events post-MI remains a major challenge. RESULTS: Here, we carried out a metagenomic analysis to characterize the systemic bacteria in a cohort of 49 healthy control individuals, 50 stable coronary heart disease (CHD) subjects, and 100 ST-segment elevation myocardial infarction (STEMI) patients. We report for the first time higher microbial richness and diversity in the systemic microbiome of STEMI patients. More than 12% of post-STEMI blood bacteria were dominated by intestinal microbiota (Lactobacillus, Bacteroides, and Streptococcus). The significantly increased product of gut bacterial translocation (LPS and D-lactate) was correlated with systemic inflammation and predicted adverse cardiovascular events. Following experimental MI, compromised left ventricle (LV) function and intestinal hypoperfusion drove gut permeability elevation through tight junction protein suppression and intestinal mucosal injury. Upon abrogation of gut bacterial translocation by antibiotic treatment, both systemic inflammation and cardiomyocyte injury in MI mice were alleviated. CONCLUSIONS: Our results provide the first evidence that cardiovascular outcomes post-MI are driven by intestinal microbiota translocation into systemic circulation. New therapeutic strategies targeting to protect the gut barrier and eliminate gut bacteria translocation may reduce or even prevent cardiovascular events post-MI.

Th17/Treg Imbalance Induced by Dietary Salt Variation Indicates Inflammation of Target Organs in Humans.

The functions of T helper 17 (Th17) and regulatory T (Treg) cells are tightly orchestrated through independent differentiation pathways that are involved in the secretion of pro- and anti-inflammatory cytokines induced by high-salt dietary. However, the role of imbalanced Th17/Treg ratio implicated in inflammation and target organ damage remains elusive. Here, by flow cytometry analysis, we demonstrated that switching to a high-salt diet resulted in decreased Th17 cells and reciprocally increased Treg cells, leading to a decreased Th17/Treg ratio. Meanwhile, Th17-related pathway was down-regulated after one day of high salt loading, with the increase in high salt loading as shown by microarray and RT-PCR. Subsequently, blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) observed hypoxia in the renal medulla (increased R2(*) signal) during high-salt loading, which was regressed to its baseline level in a step-down fashion during low-salt feeding. The flow-mediated vasodilatation (FMD) of the branchial artery was significantly higher on the first day of high salt loading. Collectively, these observations indicate that a short-term increase in dietary salt intake could induce reciprocal switches in Th17/Treg ratio and related cytokines, which might be the underlying cellular mechanism of high-salt dietary induced end organ inflammation and potential atherosclerotic risk.

The Kinetics of Circulating Monocyte Subsets and Monocyte-Platelet Aggregates in the Acute Phase of ST-Elevation Myocardial Infarction: Associations with 2-Year Cardiovascular Events.

In experimental myocardial infarction (MI), a rise in cell counts of circulating monocyte subsets contributes to impaired myocardial healing and to atherosclerotic plaque destabilization. In humans, the prognostic role of monocyte subsets in patients suffering ST-elevation MI (STEMI) is still unclear. In the present study, we aimed to determine the kinetics of the 3 monocyte subsets (classical CD14++CD16-, intermediate CD14++CD16+, and nonclassical CD14+CD16++ monocytes), as well as the subset-specific monocyte-platelet aggregates (MPA), in acute STEMI followed by primary percutaneous coronary intervention (PCI), and their relationships with cardiovascular outcomes during a 2-year follow-up.Monocyte subsets and MPA were measured in 100 STEMI patients receiving primary PCI on days 1, 2, 3, 5, and 7 of symptom onset, which were compared with 60 stable coronary heart disease patients and 35 healthy volunteers. From day 1 to day 7, significant increases in the counts of CD14++CD16+ monocytes and CD14++CD16+ MPA were observed, with peak levels on day 2. During a median follow-up of 2.0 years, 28 first cardiovascular events (defined as cardiovascular death, nonfatal ischemic stroke, recurrent MI, need for emergency or repeat revascularization, and rehospitalization for heart failure) were recorded. After adjustment for confounders, CD14++CD16+ monocytosis (day 1 [HR: 3.428; 95% CI: 1.597-7.358; P = 0.002], day 2 [HR: 4.835; 95% CI: 1.106-21.13; P = 0.04], day 3 [HR: 2.734; 95% CI: 1.138-6.564; P = 0.02], and day 7 [HR: 2.647; 95% CI: 1.196-5.861; P = 0.02]), as well as increased levels of CD14++CD16+ MPA measured on all time points (days 1, 2, 3, 5, and 7), had predictive values for adverse cardiovascular events.In conclusion, our data show the expansion of the CD14++CD16+ monocyte subset during acute phase of STEMI has predictive values for 2-year adverse cardiovascular outcomes in patients treated with primary PCI. Future studies will be warranted to elucidate whether CD14++CD16+ monocytes may become a target cell population for new therapeutic strategies after STEMI.

BOLD-MRI evaluation of subcutaneous and visceral adipose tissue oxygenation status: effect of dietary salt intake.

To investigate the feasibility of blood oxygen level dependent magnetic resonance imaging (BOLD-MRI) in evaluating human subcutaneous and visceral adipose tissue (AT) oxygenation status, as well as their responses to dietary salt loading/depletion, we enrolled 16 healthy subjects [mean body mass index (BMI): 24.8 ± 2.7 kg/m(2)] to conduct a dietary intervention study, beginning with a 3-day run-in period for usual diet, followed by a 7-day high-salt diet (≥ 15 g NaCl/day) and a 7-day low-salt diet (≤ 5 g NaCl/day). Abdominal BOLD-MRI scan was performed to evaluate oxygenation in waist subcutaneous and perirenal (visceral) AT. Two subjects with lower BMI were excluded because of the difficulty to identify subcutaneous AT. High salt diet led to a consistent increase in R2* signal (a parameter for increased hypoxia) both in subcutaneous and visceral AT (all P < 0.0001), which was completely regressed to baseline levels by low salt diet. In addition, subcutaneous AT R2* values at any time points, were all higher than that of visceral AT (all P < 0.0001). Pearson correlation analysis revealed that the visceral AT R2* levels were negatively associated obesity indicators (waist circumference, waist-to-hip ratio and BMI). On the contrary, although a trend towards negative associations between the subcutaneous AT R2* and obesity indicators was observed, none of the associations reached statistical significances. Thus, our data demonstrate the possibility of simultaneous detection of human subcutaneous and visceral AT oxygenation status using BOLD-MRI. In addition, there is a more close relationship visceral AT oxygenation status and the development of obesity.

Temporal and spatial characterization of mononuclear phagocytes in circulating, lung alveolar and interstitial compartments in a mouse model of bleomycin-induced pulmonary injury.

The mononuclear phagocyte system, including circulating monocytes and tissue resident macrophages, plays an important role in acute lung injury and fibrosis. The detailed dynamic changes of mononuclear phagocytes in the circulating, lung alveolar and interstitial compartments in bleomycin-induced pulmonary injury model have not been fully characterized. The present study was designed to address this issue and analyzed their relationships with pulmonary pathological evolution after bleomycin challenge. A total of 100 male C57BL/6 mice were randomly divided to receive bleomycin (2.5mg/kg, n=50) or normal saline (n=50) via oropharyngeal approach, and were sacrificed on days 1, 3, 7, 14 and 21. Circulating monocyte subsets, polarization state of bronchoalveolar lavage fluid (BALF)-derived alveolar macrophages (AMφ) and lung interstitial macrophages (IMφ, derived from enzymatically digested lung tissue) were analyzed by flow cytometry. There was a rapid expansion of circulating Ly6C(hi) monocytes which peaked on day 3, and its magnitude was positively associated with pulmonary inflammatory response. Moreover, an expansion of M2-like AMφ (F4/80+CD11c+CD206+) peaked on day 14, and was positively correlated with the magnitude of lung fibrosis. The polarization state of IMφ remained relatively stable in the early- and mid-stage after bleomycin challenge, expect for an increase of M2-like (F4/80+CD11c-CD206+) IMφ on day 21. These results support the notion that there is a Ly6C(hi)-monocyte-directed pulmonary AMφ alternative activation. Our result provides a dynamic view of mononuclear phagocyte change in three compartments after bleomycin challenge, which is relevant for designing new treatment strategies targeting mononuclear phagocytes in this model.

High-salt intake induced visceral adipose tissue hypoxia and its association with circulating monocyte subsets in humans.

OBJECTIVE: To investigate the feasibility of blood oxygen level dependent magnetic resonance imaging (BOLD-MRI) in evaluating human visceral adipose tissue (AT) oxygenation induced by salt loading/depletion and its association with changes in circulating monocyte subsets. METHODS: A dietary intervention study was performed in 23 healthy volunteers beginning with a 3-day usual diet followed by a 7-day high-salt diet (≥15 g NaCl/day) and a 7-day low-salt diet (≤5 g NaCl/day). BOLD-MRI was used to evaluate oxygenation in perirenal AT. RESULTS: Salt loading led to a consistent AT hypoxia (increase in the R2* signal, 25.2 ± 0.90 s(-1) vs. baseline 21.5 ± 0.71 s(-1) , P < 0.001) and suppression of circulating renin-angiotensin-aldosterone system (RAAS), as well as an expansion of the CD14++CD16+ monocytes and monocyte pro-inflammatory activation. In salt depletion phase, the hypoxic state of AT and the expanded CD14++CD16+ monocyte pool were regressed to baseline levels, accompanied by a rebound activation of RAAS. Moreover, AT oxygenation level was positively correlated with the CD14++CD16+ monocytes (r = 0.419, P < 0.001). CONCLUSIONS: This work provides proof-of-principle evidence supporting the feasibility of BOLD-MRI in monitoring visceral AT oxygenation in humans induced by dietary salt loading/depletion. In addition, the CD14++CD16+ monocytes may participate in the pathogenesis of high-salt intake induced AT hypoxia.

Variation in dietary salt intake induces coordinated dynamics of monocyte subsets and monocyte-platelet aggregates in humans: implications in end organ inflammation.

BACKGROUND: Monocyte activation and tissue infiltration are quantitatively associated with high-salt intake induced target organ inflammation. We hypothesized that high-salt challenge would induce the expansion of CD14++CD16+ monocytes, one of the three monocyte subsets with a pro-inflammatory phenotype, that is associated with target organ inflammation in humans. METHODOLOGY/PRINCIPAL FINDINGS: A dietary intervention study was performed in 20 healthy volunteers, starting with a 3-day usual diet and followed with a 7-day high-salt diet (≥15 g NaCl/day), and a 7-day low-salt diet (≤5 g NaCl/day). The amounts of three monocyte subsets ("classical" CD14++CD16-, "intermediate" CD14++CD16+ and "non-classical" CD14+CD16++) and their associations with monocyte-platelet aggregates (MPAs) were measured by flow cytometry. Blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) was used to evaluate renal hypoxia. Switching to a high-salt diet resulted in CD14++ monocyte activation and a rapid expansion of CD14++CD16+ subset and MPAs, with a reciprocal decrease in the percentages of CD14++CD16- and CD14+CD16++ subsets. In vitro study using purified CD14++ monocytes revealed that elevation in extracellular [Na(+)] could lead to CD14++CD16+ expansion via a ROS dependent manner. In addition, high-salt intake was associated with progressive hypoxia in the renal medulla (increased R2* signal) and enhanced urinary monocyte chemoattractant protein-1 (MCP-1) excretion, indicating a temporal and spatial correlation between CD14++CD16+ subset and renal inflammation. The above changes could be completely reversed by a low-salt diet, whereas blood pressure levels remained unchanged during dietary intervention. CONCLUSIONS/SIGNIFICANCE: The present work demonstrates that short-term increases in dietary salt intake could induce the expansion of CD14++CD16+ monocytes, as well as an elevation of MPAs, which might be the underlying cellular basis of high-salt induced end organ inflammation and potential thromboembolic risk. In addition, this process seems largely unrelated to changes in blood pressure levels. This finding provides novel links between dietary salt intake, innate immunity and end organ inflammation.

Spironolactone attenuates bleomycin-induced pulmonary injury partially via modulating mononuclear phagocyte phenotype switching in circulating and alveolar compartments.

BACKGROUND: Recent experimental studies provide evidence indicating that manipulation of the mononuclear phagocyte phenotype could be a feasible approach to alter the severity and persistence of pulmonary injury and fibrosis. Mineralocorticoid receptor (MR) has been reported as a target to regulate macrophage polarization. The present work was designed to investigate the therapeutic potential of MR antagonism in bleomycin-induced acute lung injury and fibrosis. METHODOLOGY/PRINCIPAL FINDINGS: We first demonstrated the expression of MR in magnetic bead-purified Ly6G-/CD11b+ circulating monocytes and in alveolar macrophages harvested in bronchoalveolar lavage fluid (BALF) from C57BL/6 mice. Then, a pharmacological intervention study using spironolactone (20 mg/kg/day by oral gavage) revealed that MR antagonism led to decreased inflammatory cell infiltration, cytokine production (downregulated monocyte chemoattractant protein-1, transforming growth factor ß1, and interleukin-1ß at mRNA and protein levels) and collagen deposition (decreased lung total hydroxyproline content and collagen positive area by Masson' trichrome staining) in bleomycin treated (2.5 mg/kg, via oropharyngeal instillation) male C57BL/6 mice. Moreover, serial flow cytometry analysis in blood, BALF and enzymatically digested lung tissue, revealed that spironolactone could partially inhibit bleomycin-induced circulating Ly6C(hi) monocyte expansion, and reduce alternative activation (F4/80+CD11c+CD206+) of mononuclear phagocyte in alveoli, whereas the phenotype of interstitial macrophage (F4/80+CD11c-) remained unaffected by spironolactone during investigation. CONCLUSIONS/SIGNIFICANCE: The present work provides the experimental evidence that spironolactone could attenuate bleomycin-induced acute pulmonary injury and fibrosis, partially via inhibition of MR-mediated circulating monocyte and alveolar macrophage phenotype switching.