Successful treatment with dupilumab in mepolizumab-resistant allergic bronchopulmonary aspergillosis.

A 67-year-old woman with a history of poorly controlled asthma was admitted to our hospital with a persistent cough and abnormal chest radiographic findings. Her diagnosis was allergic bronchopulmonary aspergillosis (ABPA). Following treatment with mepolizumab, her symptoms and imaging findings improved initially. However, after approximately 2 years, the patient experienced a recurrent cough with elevated non-specific immunoglobulin E levels and worsening chest imaging findings, thereby changing her diagnosis to recurrent ABPA. Mepolizumab was substituted with dupilumab, and her subjective symptoms and imaging findings improved. Our findings suggest that dupilumab may be effective in ABPA cases following the failure of another antibody therapy.

Prognostic value of the serum creatinine/cystatin C ratio in patients with chronic obstructive pulmonary disease.

BACKGROUND: Sarcopenia, characterized by skeletal muscle atrophy and physical inactivity, is a manifestation of chronic obstructive pulmonary disease (COPD) and is associated with a poor prognosis. The serum creatinine (Cr)/cystatin C (CysC) ratio has been proposed as a marker of sarcopenia, given its correlation with total skeletal muscle mass, and as a prognostic indicator in COPD. This study aimed to evaluate the usefulness of the serum Cr/CysC ratio as a prognostic determinant in these patients. METHODS: A total of 124 outpatients with COPD were enrolled in this study. Their serum Cr and CysC levels were measured. Survival time analyses were conducted to compare mortality rates between the low and high serum Cr/CysC ratio groups. Multivariate analysis was performed to investigate the association between various factors. RESULTS: Using a serum Cr/CysC cut-off value of 0.885, the mortality rate (per 1000 person-years) for overall mortality was significantly higher in the low serum Cr/CysC ratio group (69.2 versus 28.6; hazard ratio, 2.47; 95% confidence interval, 1.06-5.79; p < 0.05). Similarly, the mortality rate due to respiratory disease was also higher (37.8 versus 8.2; hazard ratio, 4.68; 95% confidence interval, 1.05-20.9; p < 0.05). Multivariate Cox proportional hazards analysis revealed that serum Cr/CysC was an independent risk factor for respiratory disease mortality, regardless of age and airflow limitations. CONCLUSIONS: The serum Cr/CysC ratio could be a valuable clinical parameter for identifying sarcopenia and severe airflow obstruction. The study findings highlight the utility of this ratio as a prognostic predictor in patients with COPD.

Serum Derivatives of Reactive Oxygen Metabolites are Associated with Severity of Chronic Obstructive Pulmonary Disease and Affected by a p53 Gene Polymorphism.

Purpose: Oxidative stress is known to activate tumor suppressor p53, which inhibits cell cycle progression and induces apoptosis. Levels of p53 in lung tissues from patients with chronic obstructive pulmonary disease (COPD) are increased compared with levels in nonsmokers or smokers without emphysema. A polymorphism in p53 codon 72 (rs1042522) is associated with emphysematous changes in patients with COPD. However, whether oxidative stress in the serum is associated with the p53 polymorphism and disease severity in COPD patients is unclear. Patients and Methods: A total of 251 patients with a history of smoking more than 10 pack-years were enrolled in this study, and serum levels of derivatives of reactive oxygen metabolites (d-ROMs), biological antioxidant potential (BAP), and d-ROMs/BAP ratio (oxidative stress index; OSI) were measured. The percent low-attenuation area (LAA%) and cross-sectional area of the erector spinae muscles (ESMCSA) at the Th12 level were calculated from chest high-resolution computed tomography images. p53 codon 72 C/G genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism analysis. Results: In patients carrying the p53 GG genotype, LAA% was significantly higher than in those carrying the CC genotype. d-ROM levels and OSI were associated with COPD severity and correlated with airflow limitation and markers of muscle atrophy (ESMCSA and creatinine/cystatin C ratio). Associations between markers of oxidative stress and COPD severity were observed primarily in patients carrying the p53 codon 72 GG genotype. Conclusion: Susceptibility to pulmonary emphysema and responses to oxidative stress may be affected by the p53 gene polymorphism.

Serum Creatinine/Cystatin C Ratio Associated with Cross-Sectional Area of Erector Spinae Muscles and Pulmonary Function in Patients with Chronic Obstructive Pulmonary Disease.

PURPOSE: Muscle atrophy is a major clinical feature of chronic obstructive pulmonary disease (COPD) and is considered a predictor of mortality in COPD patients. Recently, the cross-sectional area (CSA) of the erector spinae muscles measured by chest computed tomography (CT) scans (ESMCSA) has been reported as a clinical parameter reflecting disease severity and future prognosis in patients with COPD. In addition, the serum creatinine (Cr)/cystatin C (CysC) ratio has been considered a quantitative marker of residual muscle mass, because serum Cr levels are affected by muscle mass, and correction by CysC counteracts the effect of renal function on serum Cr levels. The purpose of this study was to assess whether the serum Cr level corrected by serum CysC can be used as a predictive marker of pulmonary function and disease severity in patients with COPD. PATIENTS AND METHODS: A total of 99 patients without COPD and 201 patients with COPD, with a smoking history of more than 10 pack-years were enrolled in this study, and serum Cr and CysC levels were measured. On chest high-resolution CT images, %low attenuation area (LAA%) (≤960 Hounsfield units (HU)) and ESMCSA at the Th12 level were identified. RESULTS: There was a significant correlation between the ESMCSA and the Cr/CysC ratio. The Cr/CysC ratio was significantly associated with forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) values, especially in former smokers. CONCLUSION: The serum Cr/CysC ratio could be a convenient substitute for the measurement of muscle atrophy and pulmonary function testing in patients with COPD.

ADRB2 gene polymorphism and emphysema heterogeneity can modulate bronchodilator response in patients with emphysema.

BACKGROUND: Genetic variation in the ß2-adrenergic receptor (ADRB2) gene has been thought to have an important role in the differential response to ß2-agonist therapy for asthma. However, previous studies have shown little evidence for an association between these ADRB2 variants and the bronchial dilator response (BDR) in chronic obstructive pulmonary disease (COPD) patients. This discrepancy could be explained by differences in the distribution and heterogeneity of pulmonary emphysema in COPD patients, since emphysema distribution and heterogeneity are thought to have a role in pulmonary function in COPD patients. We hypothesized that differences in emphysema distribution and heterogeneity may have masked significant alterations of the bronchodilator response among ADRB2 genotypes in COPD patients in previous studies. METHODS: The BDR (induced by 20 µg of procaterol) was measured in 211 patients who had a smoking history of more than 10 pack/years and had undergone chest high resolution computed tomography examination. A low attenuations area (<960 Hounsfield Units) was identified and the emphysema heterogeneity index (EHI%) was calculated with a range in value from -100% to 100%. ADRB2 Arg16Gly genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism analysis. RESULTS: The BDR was augmented in patients with homogenous emphysema compared with those with upper-dominant emphysema. In patients carrying the AA genotype of ADRB2, the BDR was significantly increased in patients with upper-dominant emphysema, but not in patients with lower-dominant emphysema. CONCLUSION: Combination analysis of ADRB2 Arg16Gly polymorphism and EHI% may predict the effectiveness of ß2-adrenergic receptor agonist treatment in patients with COPD and emphysema.

p53 Signaling Pathway Polymorphisms Associated With Emphysematous Changes in Patients With COPD.

BACKGROUND: The p53 signaling pathway may be important for the pathogenesis of emphysematous changes in the lungs of smokers. Polymorphism of p53 at codon 72 is known to affect apoptotic effector proteins, and the polymorphism of mouse double minute 2 homolog (MDM2) single nucleotide polymorphism (SNP)309 is known to increase MDM2 expression. The aim of this study was to assess polymorphisms of the p53 and MDM2 genes in smokers and confirm the role of SNPs in these genes in the pathogenesis of pulmonary emphysema. METHODS: This study included 365 patients with a smoking history, and the polymorphisms of p53 and MDM2 genes were identified. The degree of pulmonary emphysema was determined by means of CT scanning. SNPs, MDM2 mRNA, and p53 protein levels were assessed in human lung tissues from smokers. Plasmids encoding p53 and MDM2 SNPs were used to transfect human lung fibroblasts (HLFs) with or without cigarette smoke extract (CSE), and the effects on cell proliferation and MDM2 promoter activity were measured. RESULTS: The polymorphisms of the p53 and MDM2 genes were associated with emphysematous changes in the lung and were also associated with p53 protein and MDM2 mRNA expression in the lung tissue samples. Transfection with a p53 gene-coding plasmid regulated HLF proliferation, and the analysis of P2 promoter activity in MDM2 SNP309-coding HLFs showed the promoter activity was altered by CSE. CONCLUSIONS: Our data demonstrated that p53 and MDM2 gene polymorphisms are associated with apoptotic signaling and smoking-related emphysematous changes in lungs from smokers.

Sirt1 expression is associated with CD31 expression in blood cells from patients with chronic obstructive pulmonary disease.

BACKGROUND: Cigarette smoke induced oxidative stress has been shown to reduce silent information regulator 1 (Sirt1) levels in lung tissue from smokers and patients with COPD patients. Sirt1 is known to inhibit endothelial senescence and may play a protective role in vascular cells. Endothelial progenitor cells (EPCs) are mobilized into circulation under various pathophysiological conditions, and are thought to play an important role in tissue repair in chronic obstructive lung disease (COPD). Therefore, Sirt1 and EPC-associated mRNAs were measured in blood samples from patients with COPD and from cultured CD34+ progenitor cells to examine whether these genes are associated with COPD development. METHODS: This study included 358 patients with a smoking history of more than 10 pack-years. RNA was extracted from blood samples and from CD34+ progenitor cells treated with cigarette smoke extract (CSE), followed by assessment of CD31, CD34, Sirt1 mRNA, miR-34a, and miR-126-3p expression by real-time RT-PCR. RESULTS: The expression of CD31, CD34, Sirt1 mRNAs, and miR-126-3p decreased and that of miR-34a increased in moderate COPD compared with that in control smokers. However, no significant differences in these genes were observed in blood cells from patients with severe COPD compared with those in control smokers. CSE significantly decreased Sirt1 and increased miR-34a expression in cultured progenitor cells. CONCLUSION: Sirt1 expression in blood cells from patients with COPD could be a biomarker for disease stability in patients with moderate COPD. MiR-34a may participate in apoptosis and/or senescence of EPCs in smokers. Decreased expression of CD31, CD34, and miR-126-3p potentially represents decreased numbers of EPCs in blood cell from patients with COPD.

Prognostic Value of Dual-Time-Point 18F-FDG PET for Idiopathic Pulmonary Fibrosis.

UNLABELLED: The aim of this prospective study was to clarify whether dual-time-point (18)F-FDG PET imaging results are useful to predict long-term survival of idiopathic pulmonary fibrosis (IPF) patients. METHODS: Fifty IPF patients underwent (18)F-FDG PET examinations at 2 time points: 60 min (early imaging) and 180 min (delayed imaging) after (18)F-FDG injection. The standardized uptake value (SUV) at each point and retention index value (RI-SUV) calculated from those were evaluated, and then the results were compared with overall and progression-free survival. RESULTS: A multivariate Cox proportional hazards model showed higher RI-SUV and higher extent of fibrosis score as independent predictors of shorter progression-free survival. The median progression-free survival for patients with negative RI-SUV was better than that for those with positive RI-SUV (27.9 vs. 13.3 mo, P = 0.0002). On the other hand, multivariate Cox analysis showed higher RI-SUV and lower forced vital capacity to be independent predictors of shorter overall survival. The 5-y survival rate for patients with negative RI-SUV was better than that for those with positive RI-SUV (76.8% vs. 14.3%, P = 0.00001). In addition, a univariate Cox model showed that positive RI-SUV as a binary variable was a significant indicator of mortality (hazard ratio, 7.31; 95% confidence interval, 2.64-20.3; P = 0.0001). CONCLUSION: Our results demonstrate that positive RI-SUV is strongly predictive of earlier deterioration of pulmonary function and higher mortality in patients with IPF.

Endogenous Asymmetric Dimethylarginine Pathway in High Altitude Adapted Yaks.

Hypoxia-induced and high altitude pulmonary hypertension are a major problem in the mountain areas of the world. The asymmetric methylarginines (ADMA) inhibit nitric oxide (NO) synthesis by competing with L-arginine, and high levels of plasma ADMA predict adverse outcomes in pulmonary hypertension. However, little is known about the regulation of the ADMA-NO pathway in animals adapted to high altitudes. We measured the plasma ADMA concentration, endothelial NO synthase (eNOS), dimethylarginine dimethylaminohydrolases (DDAH) protein expression, and DDAH activities in the lungs from yaks. Although the yaks are hypoxemic, cardiac function and pulmonary arterial pressures are almost normal, and we found decreased DDAH expression and activity in association with reduced plasma ADMA concentrations. The eNOS expression was significantly higher in yaks. These results indicate that augmented endogenous NO activity in yaks through the ADMA-DDAH pathway and eNOS upregulation account for the low pulmonary vascular tone observed in high altitude adapted yaks.

Blunted activation of Rho-kinase in yak pulmonary circulation.

Yaks have adapted to high altitude and they do not develop hypoxic pulmonary hypertension. Although we previously identified the important role of augmented nitric oxide synthase activity in the yak pulmonary circulatory system, evidence of the direct involvement of Rho-kinase as a basal vascular tone regulator is lacking. Four domesticated male pure-bred yaks and four bulls that were born and raised at an altitude of 3000 m in the Tien-Shan mountains were studied at an altitude of 3,100 m. Mean pulmonary artery pressure (mPAP) was measured before and after fasudil (60 mg in 20 mL of saline) was intravenously administered using a Swan-Ganz catheter at a rate of 3.3 mL/min for 30 min. Fasudil decreased mPAP in bulls from 67.8±14.9 to 32.3±5.3 mmHg (P < 0.05) after 15 min and the level was maintained for 30 min, but it merely blunted mPAP in yaks from 28.2±4.5 to 25.1±11.1 and 23.2±2.7 mmHg after 5 and 30 min, respectively. These findings comprise the first evidence of a modest role of Rho-kinase in the maintenance of pulmonary artery pressure in the yak.

The effects of concomitant GERD, dyspepsia, and rhinosinusitis on asthma symptoms and FeNO in asthmatic patients taking controller medications.

BACKGROUND: Losing the sense of smell, which suggests eosinophilic rhinosinusitis, is a subjective symptom, sometimes reported in asthmatic patients taking controller medication. Upper abdominal symptoms, suggesting gastroesophageal reflux disease (GERD) or functional dyspepsia, occur also in these patients. However, the relationship between these symptoms, concomitant with asthma, and the intensity of eosinophilic airway inflammation remains obscure. OBJECTIVE: To assess the symptoms of asthma and rhinosinusitis, and to examine the relationship between the symptoms and bronchial inflammation, a new questionnaire, the G scale, was developed. To investigate the effects of GERD, dyspepsia, and rhinosinusitis on asthma symptoms and bronchial inflammation, the symptoms of asthma and rhinosinusitis obtained by the G scale, upper abdominal symptoms obtained by the modified F scale, a questionnaire for GERD and dyspepsia, and fractional exhaled nitric oxide (FeNO) were analyzed. METHODS: A prospective, observational study was performed in four hospitals in Gunma prefecture, and a retrospective analysis was done using data obtained from five hospitals in Gunma prefecture and Fukui prefecture, Japan. A total of 252 patients diagnosed as having asthma participated in the prospective study. RESULTS: The frequency of daytime phlegm or losing the sense of smell had a positive correlation with FeNO levels in asthmatic patients taking controller medication. Upper abdominal symptoms, as well as symptoms suggesting rhinitis, were well correlated with asthma symptoms. However, neither upper abdominal symptoms nor rhinitis symptoms increased FeNO levels, which reflect eosinophilic airway inflammation during treatment for asthma. On the other hand, the degree of upper abdominal symptoms or dyspepsia symptoms had a weak but significant negative correlation with FeNO levels. CONCLUSION: Daytime phlegm and losing the sense of smell suggest that eosinophilic airway inflammation persists, despite anti-inflammatory therapy, in patients with asthma. Although rhinitis and GERD made the subjective symptoms of asthma worse, they did not seem to enhance eosinophilic airway inflammation.

(18)F-FDG uptake predicts diagnostic yield of transbronchial biopsy in peripheral lung cancer.

OBJECTIVES: Recent advances in endobronchial ultrasonography with a guide sheath (EBUS-GS) have enabled better visualization of distal airways, while virtual bronchoscopic navigation (VBN) has been shown useful as a guide to navigate the bronchoscope. However, indications for utilizing VBN and EBUS-GS are not always clear. To clarify indications for a bronchoscopic examination using VBN and EBUS-GS, we evaluated factors that predict the diagnostic yield of a transbronchial biopsy (TBB) procedure for peripheral lung cancer (PLC) lesions. METHODS: We retrospectively reviewed the charts of 194 patients with 201 PLC lesions (≤3cm mean diameter), and analyzed the association of diagnostic yield of TBB with [(18)F]-fluoro-2-deoxy-d-glucose ((18)F-FDG) positron emission tomography and chest computed tomography (CT) findings. RESULTS: The diagnostic yield of TBB using VBN and EBUS-GS was 66.7%. High maximum standardized uptake value (SUVmax), positive bronchus sign, and ground-glass opacity component shown on CT were all significant predictors of diagnostic yield, while multivariate analysis showed only high (18)F-FDG uptake (SUVmax ≥2.8) and positive bronchus sign as significant predictors. Diagnostic yield was higher for PLC lesions with high (18)F-FDG uptake (SUVmax ≥2.8) and positive bronchus sign (84.6%) than for those with SUVmax <2.8 and negative bronchus sign (33.3%). High (18)F-FDG uptake was also correlated with tumor invasiveness. CONCLUSIONS: High (18)F-FDG uptake predicted the diagnostic yield of TBB using VBN and EBUS-GS for PLC lesions. (18)F-FDG uptake and bronchus sign may indicate for the accurate application of bronchoscopy with those modalities for diagnosing PLC.

Bosentan reduces pulmonary artery pressure in high altitude residents.

UNLABELLED: Endothelin-1 (ET-1) plays a critical role in the regulation of pulmonary vascular tone. The aim of this study was to investigate the role of ET-1 in the pathogenesis of high altitude pulmonary arterial hypertension (HAPH). METHODS: Pulmonary artery pressure (PAP) was measured by echocardiography in permanent residents of the Kyrgyz Republic (3200-4000 m above sea level) both before and 3 h after a single oral dose of ET receptor antagonist, bosentan (125 mg). Plasma ET-1 levels were measured by ELISA assay. Genomic DNA was extracted from peripheral blood samples and the frequency of -3a and -4a alleles of the ET-1 gene determined by PCR. RESULTS: Plasma ET-1 in HAPH highlanders was significantly higher than in healthy subjects (7.05±2.35 vs. 4.65±1.65 pg/ml, p<0.002). After the treatment with 125 mg bosentan, systolic PAP decreased from 46±1.9 to 37±2.2 mm Hg (p<0.01), and pulmonary artery acceleration time (PAAT) increased from 0.086±0.001 to 0.098±0.001 sec (p<0.001). The frequency of the -4a allele was significantly higher in HAPH patients compared to healthy highlanders (0.43 vs. 0.3, χ(2)=4.3, p=0.03). CONCLUSION: Increased ET-1 levels play an important role in development of HAPH.

Small airway disease associated with Sjögren's syndrome: clinico-pathological correlations.

BACKGROUND: Relationships among clinical, physiological, imaging and pathological findings of small airway disease associated with Sjögren's syndrome have remained unclear. SUBJECTS AND METHODS: We retrospectively studied 14 patients who underwent surgical lung biopsy and who were diagnosed with small airway disease associated with primary or secondary Sjögren's syndrome. We compared clinical, bronchoalveolar lavage, physiological, imaging and pathological findings between primary and secondary Sjögren's syndrome. We scored HRCT and pathological abnormalities and investigated correlations among physiological, HRCT and pathological data, changes in physiological parameters and in HRCT scores after two years of treatment, as well as correlations between these values and pathological scores. RESULTS: Bronchoalveolar lavage fluid, physiological, imaging and pathological findings of the airways did not significantly differ between primary and secondary Sjögren's syndrome. Air trapping on HRCT negatively correlated with MEF50 and MEF25. Although lymphoid cell infiltration and peribronchiolar fibrosis were the most common pathologies, constrictive change scores correlated negatively with MEF50 and MEF25, positively with air trapping scores and negatively with improvements after therapy in MEF(50), MEF(25) and air trapping. CONCLUSIONS: Constrictive change was the most significant determinant of physiological and imaging presentations and of changes in these factors after therapy for small airway disease associated with Sjögren's syndrome.

Prognostic value of dual-time-point 18F-fluorodeoxyglucose positron emission tomography in patients with pulmonary sarcoidosis.

BACKGROUND AND OBJECTIVE: The value of dual-time- point (18) F-FDG PET was investigated to predict the prognosis of patients with pulmonary sarcoidosis. METHODS: Twenty-one patients with pulmonary sarcoidosis underwent (18) F-FDG PET examinations at two time points: an early scan at 60min and a delayed scan at 180min after injection of (18) F-FDG. Standardized uptake values (SUVs) at the two time points and the retention index (RI-SUV) calculated from these were evaluated. To evaluate disease progression, all patients underwent chest CT 1year after (18) F-FDG PET. Using these results, the accuracy of (18) F-FDG PET parameters and (67) Ga uptake for predicting disease persistence were compared, and the correlations between those parameters and serum markers were assessed. RESULTS: RI-SUV was significantly higher in patients with increased or unchanged pulmonary lesions at follow-up CT (persistent group; 21.3±9.6%) than in patients with improved pulmonary lesions (improved group; -9.2±28.6%, P=0.0075). The diagnostic accuracy of RI-SUV in the persistent group was significantly greater than that of early SUV or (67) Ga uptake, and serum soluble IL-2 receptor showed a significant correlation with RI-SUV. CONCLUSIONS: RI-SUV showed better diagnostic accuracy compared with early SUV or (67) Ga uptake, in patients with persistent lung involvement at 1year. It may be a useful measure of persistent inflammation in patients with pulmonary sarcoidosis.

Changes in aromatase (CYP19) gene promoter usage in non-small cell lung cancer.

In humans, aromatase (CYP19) gene expression is regulated via alternative promoters. Activation of each promoter gives rise to a CYP19 mRNA species with a unique 5'-untranslated region. Inhibition of aromatase has been reported to downregulate lung tumor growth. The genetic basis for CYP19 gene expression and aromatase activity in lung cancer remains poorly understood. We analyzed tissues from 15 patients with non-small cell lung cancer (NSCLC) to evaluate CYP19 promoter usage and promoter-specific aromatase mRNA levels in NSCLC tumor tissues and adjacent non-malignant tissues. CYP19 promoter usage was determined by multiplex RT-PCR and aromatase mRNA levels were measured with real-time RT-PCR. In non-malignant tissues, aromatase mRNA was primarily derived from activation of CYP19 promoter I.4. Although promoter I.4 usage was also dominant in tumor tissues, I.4 activation was significantly lower compared with adjacent non-malignant tissues. Activity of promoters I.3, I.1 and I.7 was significantly higher in tumor tissues compared with non-malignant tissues. In 4 of 15 cases of non-small cell lung cancer, switching from CYP19 promoter I.4 to the alternative promoters II, I.1 or I.7 was observed. In 9 cases, there were significantly higher levels of aromatase mRNA in lung tumor tissues compared with adjacent non-malignant tissues. These findings suggest aberrant activation of alternative CYP19 promoters that may lead to upregulation of local aromatase expression in some cases of NSCLC. Further studies are needed to examine the impact of alternative CYP19 promoter usage on local estrogen levels and lung tumor growth.

p53 Gene deficiency promotes hypoxia-induced pulmonary hypertension and vascular remodeling in mice.

Chronic hypoxia induces pulmonary arterial remodeling, resulting in pulmonary hypertension and right ventricular hypertrophy. Hypoxia has been implicated as a physiological stimulus for p53 induction and hypoxia-inducible factor-1α (HIF-1α). However, the subcellular interactions between hypoxic exposure and expression of p53 and HIF-1α remain unclear. To examine the role of p53 and HIF-1α expression on hypoxia-induced pulmonary arterial remodeling, wild-type (WT) and p53 knockout (p53KO) mice were exposed to either normoxia or hypoxia for 8 wk. Following chronic hypoxia, both genotypes demonstrated elevated right ventricular pressures, right ventricular hypertrophy as measured by the ratio of the right ventricle to the left ventricle plus septum weights, and vascular remodeling. However, the right ventricular systolic pressures, the ratio of the right ventricle to the left ventricle plus septum weights, and the medial wall thickness of small vessels were significantly greater in the p53KO mice than in the WT mice. The p53KO mice had lower levels of p21 and miR34a expression, and higher levels of HIF-1α, VEGF, and PDGF expression than WT mice following chronic hypoxic exposure. This was associated with a higher proliferating cell nuclear antigen expression of pulmonary artery in p53KO mice. We conclude that p53 plays a critical role in the mitigation of hypoxia-induced small pulmonary arterial remodeling. By interacting with p21 and HIF-1α, p53 may suppress hypoxic pulmonary arterial remodeling and pulmonary arterial smooth muscle cell proliferation under hypoxia.