Abstract
Background
Acute respiratory distress syndrome (ARDS) is a heterogeneous clinical syndrome with high morbidity and mortality. Despite advances in understanding its pathophysiology, definitive biomarkers for ARDS disease stratification and management remain lacking. This study evaluated the utility of circulating PRDX1 in predicting 28-day mortality in ARDS patients.
Methods
A retrospective cohort study was conducted at Third Xiangya Hospital, enrolling 90 ARDS patients. Serum PRDX1 levels and clinical data were collected and compared with those from healthy volunteers and non-ARDS pneumonia patients to examine its alterations in ARDS patients; multivariate logistic regression and receiver operating characteristic (ROC) curve analyses were then employed to assess the prognostic value of circulating PRDX1 for 28-day mortality. An independent validation cohort of 20 ARDS patients was recruited from Xiangya Hospital intensive care units. Additionally, serum Prdx1 dynamics were assessed in LPS-induced acute lung injury (ALI) and sepsis-associated ALI murine models.
Results
Serum PRDX1 levels were significantly elevated in a cohort of 90 ARDS patients, particularly among those with multiorgan injury. Multivariate analysis identified PRDX1 and age as independent risk factors for 28-day mortality. ROC curves revealed PRDX1’s prognostic utility (area under the curve, AUC=0.776, p<0.0001), which was comparable to the APACHE II score (AUC=0.778, p<0.0001). These findings were validated in the 20-patient cohort. Animal experiments confirmed that serum PRDX1 positively correlated with lung injury severity and exhibited earlier elevation and higher abundance in multiorgan injury contexts.
Conclusions
Serum PRDX1 was significantly elevated in ARDS patients, particularly in those with multiorgan injury, and demonstrated potential as a prognostic biomarker, showing correlation with 28-day mortality. Its integration into the ARDS management framework holds significant potential for improving clinical outcomes.
Keywords: ARDS
WHAT IS ALREADY KNOWN ON THIS TOPIC
A critical need exists for reliable biomarkers in acute respiratory distress syndrome (ARDS), a condition with high mortality. While extracellular Prdx1 is recognised as a pro-inflammatory damage-associated molecular pattern molecule involved in acute organ injury, its role as a biomarker in ARDS remains unestablished.
WHAT THIS STUDY ADDS
This study reveals that circulating PRDX1 is significantly elevated in ARDS patients and serves as an independent predictor of 28-day mortality. Its prognostic performance is comparable to the Acute Physiology and Chronic Health Evaluation II score.
HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY
These results position circulating PRDX1 as a candidate biomarker for improving risk stratification and prognostic assessment in ARDS, potentially aiding in early triage and personalised management in critical care settings.
Introduction
Acute respiratory distress syndrome (ARDS) is a heterogeneous clinical syndrome typically triggered by pulmonary factors (eg, bacterial/fungal infections) or extrapulmonary insults (extrapulmonary sepsis, trauma, transfusion, etc). It is clinically characterised by progressive dyspnoea, tachypnoea and hypoxaemia, rapidly evolving into respiratory failure.1 ARDS diagnosis relies on combined clinical and pathophysiological evaluation.2 3 However, clinicians often face challenges in systematically fulfilling diagnostic criteria requiring integration of clinical, biological and radiological features, particularly given ARDS patients’ frequent comorbidities or critical illness status.4 The landmark international LUNG SAFE study, the largest ARDS patient cohort to date, revealed substantial underrecognition and delayed diagnosis of ARDS.5 Failure to promptly identify ARDS precludes timely implementation of survival-enhancing therapeutic strategies, underscoring the critical importance of early diagnosis. Despite advances in ARDS management, its incidence remains alarmingly high in intensive care units (ICUs), with mortality rates for severe ARDS exceeding 40%.5
Considerable clinical heterogeneity exists among ARDS patients across aetiology, pathophysiology, clinical manifestations, therapeutic responses and outcomes. This heterogeneity has led to the failure of multiple promising therapeutic agents in clinical trials. Consequently, growing research focuses on identifying refined ARDS subphenotypes to enable targeted interventions.6 Pathophysiology-associated biomarkers hold significant potential in ARDS research, as they may provide insights into disease severity, progression and treatment responsiveness.7 Nevertheless, validated biomarkers for early diagnosis and prognostic assessment in ARDS patients remain an unmet clinical need.
Peroxiredoxin 1 (Prdx1), a member of the peroxiredoxin family, is predominantly expressed in the cytoplasm where it exerts critical antioxidant functions and is widely distributed across human cells and organs. Recent studies indicate that Prdx1 can be secreted extracellularly following cellular injury. Extracellular Prdx1 acts as a novel damage-associated molecular pattern (DAMP), capable of binding to pattern recognition receptors (PRRs) such as TLR2/4 and Mincle, thereby activating innate immune responses and promoting inflammation.8 9 Our previous investigations demonstrated associations between serum PRDX1 levels and acute organ injuries. Specifically, elevated serum PRDX1 concentrations were observed in patients with acute kidney injury and hepatic failure.9 10 However, the relationship between PRDX1 and ARDS remains unexplored.
In this study, we aim to investigate changes and clinical utility of PRDX1 in ARDS patients, with the goal of identifying novel targets for early diagnosis and prognostic prediction in ARDS management.
Methods
Materials
Lipopolysaccharide (LPS, Escherichia coli O111:B4, #L2630) was obtained from Sigma-Aldrich (MA, USA). ELISA kits for human IL-6 (#JL14113), MCP-1 (#JL19334) and PRDX1 (#JL19445) were sourced from Jianglai Biotech (Shanghai, China), while mouse Prdx1 (#CSB-EL018653MO) was purchased from CUSABIO (Wuhan, China).
Human subjects
We collected blood samples and clinical data from ARDS patients admitted to the Respiratory Intensive Care Unit (RICU) at the Third Xiangya Hospital of Central South University from January to December 2024, with 28-day mortality follow-up after RICU admission. Adult patients (>18 years) meeting ARDS diagnostic criteria were eligible for inclusion. Exclusion criteria included pregnancy, malignancy, transplant recipients (solid organ or haematopoietic stem cell transplantation), immunodeficiency, long-term use of corticosteroids or immunosuppressants, and cases with incomplete data. Among 124 ARDS patients admitted to RICU from January 2024 to December 2024, 34 were excluded based on exclusion criteria, leaving 90 patients for final analysis. Healthy controls were recruited from the health examination centre of the same hospital, while non-ARDS pneumonia patients were obtained from the Department of Respiratory and Critical Care Medicine. Using identical exclusion criteria, we collected and ultimately included 13 non-ARDS patients from the RICU. This cohort consisted of patients with cardiogenic pulmonary oedema, pleural effusion, acute exacerbation of chronic obstructive pulmonary disease (COPD) and severe asthma. Blood samples were collected from ARDS and non-ARDS patients within 24 hours after diagnosis.
An independent validation cohort of 20 ARDS patients was subsequently collected from the ICU of Xiangya Hospital, Central South University, between September 2024 and December 2024, using identical inclusion/exclusion criteria.
A team of experienced respiratory clinicians independently extracted data from electronic medical records. Demographic and clinical characteristics within 24 hours of ICU admission were collected, including age, gender, smoking history, comorbidities, oxygenation index (PaO2/FiO2, ratio of partial pressure of arterial oxygen to fraction of inspired oxygen), aetiology, Sequential Organ Failure Assessment (SOFA) score, Acute Physiology and Chronic Health Evaluation (APACHE II) score, and laboratory parameters (complete blood count, biochemical profile, Coagulation Function, CRP and PCT). ARDS was diagnosed according to the criteria set forth in the latest guidelines: A New Global Definition of Acute Respiratory Distress Syndrome.3 The enrolled ARDS patients were diagnosed according to the Berlin Definition criteria.
Human blood serum collection
Blood samples were centrifuged (1000 rpm, 10 min, 4℃) within 30 min of sample collection and stored at –80℃ for subsequent analysis.
Animal models
Wild-type male C57BL/6J mice (8–10 weeks, Silaike Co.) were housed under SPF conditions (12-hour light/dark cycle). At the end of the experiment, the animals were euthanised, and blood samples and lung tissue were collected for subsequent experiments.
ELISA
The concentrations of PRDX1, IL-6 and MCP-1 in human or murine serum were measured using the corresponding ELISA kits according to the manufacturer’s instructions.
Histopathology
The mouse lung tissue was excised, with the right lung preserved in liquid nitrogen for future use, while the left lung was fixed in 4% paraformaldehyde. The fixed left lung was then embedded in paraffin and sectioned into 4μm-thick slices, which were stained with H&E. The H&E-stained sections were subsequently observed under a light microscope at 200× magnification. A semi-quantitative pathological scoring was conducted based on established scoring criteria to evaluate the degree of inflammatory cell infiltration, alveolar structure disruption and congestion in the lung tissue, with scores ranging from 0 to 4. 10 random fields were assessed for each slide.11 Histopathological scores for lung tissue were independently assessed by three blinded pathologists. The final score for each sample was derived as the mean of the three individual scores.
Statistical analysis
Categorical variables are presented as counts (percentages), and continuous variables as mean±SD or median with IQR. Differences between groups were assessed using the χ² test, Fisher’s exact test, Student’s t-test or Mann-Whitney U test, as appropriate. For predictive performance and receiver operating characteristic (ROC) curve analysis: All predictors, including serum PRDX1 levels and APACHE II scores, were analysed as continuous variables. To evaluate the combined predictive value of PRDX1 and APACHE II for clinical outcomes 28-day mortality, we first constructed a binary logistic regression model with the outcome as the dependent variable and both continuous predictors as covariates. From this model, the predicted probability for each patient was saved as a new variable, which served as the continuous composite predictor ‘PRDX1+APACHE II’ for subsequent analysis. The discriminatory performance of individual predictors (PRDX1, APACHE II) and the combined predictor was assessed by generating ROC curves and calculating the area under the curve (AUC). ROC analysis was performed using the ‘ROC Curve’ procedure in SPSS. The optimal cut-off point for a single predictor was determined by maximising the Youden index (J). Statistical comparison of the ROC curves was performed using the DeLong test/Bootstrap method. Correlations between continuous variables were analysed using Pearson correlation coefficient. For variables with skewed distributions (assessed via Shapiro-Wilk test or visual inspection of histograms), a base-10 logarithmic (log10) transformation was applied prior to correlation and linear regression analyses, and the results are reported based on the transformed data. Multivariable logistic regression models were used to assess the prognostic value of PRDX1 for mortality, adjusted for potential confounders including age, sex, PCT, SCr, SOFA score and APACHE II score. In animal experiments, comparisons between two groups were performed using Student’s t-test and one-way analysis of variance was applied for multigroup comparisons. All statistical analyses were conducted using SPSS (V.22.0; IBM). Statistical significance was defined as p<0.05 (*p<0.05, **p<0.01, ***p<0.001, ****p<0.0001).
Result
Elevated circulating PRDX1 levels are associated with prognosis in ARDS patients
Characteristics of the study cohort
We consecutively screened 124 ARDS patients admitted to the RICU at the Third Xiangya Hospital, excluding 34 patients based on predefined exclusion criteria, ultimately enrolling 90 ARDS patients (online supplemental figure S1). Follow-up for 28-day mortality post-RICU admission revealed a mortality rate of 48.9% (44/90). In addition to ARDS patients, we recruited 30 healthy volunteers and 30 non-ARDS pneumonia patients. We also conducted a 28-day mortality follow-up for non-ARDS patients after admission and observed no mortality. Demographic and clinical characteristics are summarised in online supplemental tables S1 and S2.
Compared with non-ARDS pneumonia patients, ARDS patients were significantly older (p=0.01), while no significant differences were observed in gender, smoking history or comorbidities between the two groups (online supplemental table S1). The most prevalent comorbidities in both groups were COPD and cardiovascular diseases, consistent with prior studies, reflecting the high prevalence of these conditions in China and underscoring the urgency of chronic disease management. No significant differences in aetiological distribution were identified between the groups, with bacterial infection predominating, followed by fungal and viral infections, as well as extrapulmonary factors (online supplemental table S1).
Regarding laboratory parameters, ARDS patients exhibited significantly lower lymphocyte counts and Hb levels, alongside elevated alanine aminotransferase, aspartate aminotransferase, serum creatinine (Scr), blood urea nitrogen (BUN), activated partial thromboplastin time and D-dimer levels (p<0.05 for all), indicating greater disease severity and frequent multiorgan involvement in ARDS (online supplemental table S2). In terms of disease severity, ARDS patients demonstrated a significantly lower PaO2/FiO2 ratio compared with non-ARDS pneumonia patients (online supplemental table S1).
ARDS patients show significantly elevated circulating PRDX1 levels
Circulating levels of PRDX1 are theoretically closely associated with the extent and severity of cellular injury. According to the Human Protein Atlas database, PRDX1 is abundantly expressed across multiple organs, with medium expression levels observed in the trachea and lung tissues (figure 1A). In our study, we measured serum PRDX1 concentrations in healthy volunteers, non-ARDS pneumonia patients and ARDS patients. compared with healthy volunteers and non-ARDS pneumonia patients, ARDS patients exhibited significantly elevated serum PRDX1 levels (figure 1B), suggesting its potential as a diagnostic biomarker for ARDS. To further evaluate whether serum PRDX1 could serve as a diagnostic biomarker for ARDS, we conducted a more detailed reanalysis of figure 1B. Given that prior studies have reported PRDX1 release during extrapulmonary organ injury8,10 (eg, liver, brain, kidney), we assessed the contribution of isolated lung injury to circulating PRDX1 levels. Results showed that ARDS patients with isolated lung injury showed an upward trend in serum PRDX1 compared with non-ARDS pneumonia patients, but the difference was not statistically significant. Additionally, we measured serum PRDX1 in a separate cohort of non-ARDS patients from the RICU. Again, no significant difference was observed between ARDS patients with isolated lung injury and these non-ARDS patients (figure 1C). These data indicate that elevated serum PRDX1 reflects disease severity or the presence of multi-organ injury in ARDS patients, rather than functioning as a diagnostic biomarker for ARDS itself.
Figure 1. ARDS patients show significantly elevated circulating PRDX1 levels. (A) Expression of PRDX1 in different tissues, data obtained from the Human Protein Atlas. PRDX1 is expressed across multiple organs. (B) Serum PRDX1 concentrations at admission measured by ELISA in healthy volunteers (n=30), non-ARDS pneumonia patients (n=30) and ARDS patients (n=90). (C) Serum PRDX1 concentrations measured by ELISA in healthy volunteers, non-ARDS pneumonia patients, ARDS-lung patients, ARDS-lung+multiorgan failure patients and non-ARDS patients in RICU. ARDS-lung patients mean ARDS patients with isolated pulmonary injury. ARDS, acute respiratory distress syndrome; HV, healthy volunteers; RICU, respiratory intensive care unit.
Correlation analysis of circulating PRDX1 with clinical characteristics in ARDS patients
Among ARDS patients, the most prevalent comorbidities were cardiovascular disorders (including atrial fibrillation and coronary heart disease), hypertension, diabetes mellitus and COPD. Non-survivors were significantly older than survivors (p<0.001), while no significant differences were observed in gender, smoking history or comorbidities between the two groups (online supplemental table S1). Among ARDS patients, the primary aetiology of ARDS was bacterial infection (51.1% of cases), followed by viral infection (23.3%). A minority of cases were attributed to pancreatitis or aspiration, while 5.6% of patients exhibited no identifiable pathogen or specific aetiology (online supplemental table S1). Laboratory parameters (online supplemental table S2) revealed higher Scr (p=0.022) and BUN (p<0.001) levels in non-survivors. For inflammatory markers (online supplemental table S1), non-survivors exhibited significantly elevated CRP (p=0.041), PCT (p=0.031) and PRDX1 (p<0.001) levels. Regarding disease severity (online supplemental table S1), non-survivors demonstrated a lower PaO2/FiO2 ratio (143 (107.25–168) vs 94 (72–129), p=0.001), higher SOFA scores (3.5 (3-5) vs 6 (4–7.25), p<0.001) and elevated APACHE II scores (10 (7.25–14.75) vs 15.5 (13–19.25), p<0.001).
We assessed associations between PRDX1 and inflammatory cytokines as well as disease severity. Serum PRDX1 demonstrated positive correlations with TNF-α, IL-6, MCP-1, CRP, SOFA scores and APACHE II scores (figure 2A–F). Elevated inflammatory levels and higher disease severity scores are established predictors of adverse outcomes in ARDS. The observed positive correlations between PRDX1 and these prognostic factors suggest its potential utility in predicting clinical outcomes in ARDS patients.
Figure 2. Correlation analysis between circulating PRDX1 levels and clinical parameters in ARDS patients. (A–F) Correlation analysis between serum PRDX1 levels and clinical parameters in ARDS patients: (C) TNF-α, (D) MCP-1, (E) IL-6, (F) CRP, (G) APACHE II score, (H) SOFA score. (G) Association between serum PRDX1 levels and the number of injured organs in ARDS patients. APACHE II, Acute Physiology and Chronic Health Evaluation; ARDS, acute respiratory distress syndrome; CRP, C reactive protein; SOFA, Sequential Organ Failure Assessment.
Given that ARDS patients often present with acute injuries to other organs or systems, where multiorgan dysfunction is strongly associated with poor outcomes—and considering prior evidence of elevated circulating PRDX1 in conditions such as stroke and acute liver/kidney injury, we evaluated the relationship between PRDX1 and multiorgan injury using the SOFA criteria. Patients with ≥3 organ injuries exhibited significantly higher serum PRDX1 levels (figure 2G).
Circulating PRDX1 and 28-Day mortality
Subsequently, we performed univariate and multivariate analyses to evaluate the association between PRDX1 and 28-day mortality in ARDS patients. Both PRDX1 and age were identified as independent risk factors for mortality (online supplemental table S3, figure 3A). Non-survivors exhibited significantly higher serum PRDX1 levels compared with survivors (p<0.001; figure 3B). We further assessed the predictive performance of PRDX1 for 28-day mortality. The APACHE II score, a validated tool for assessing disease severity and predicting mortality in critically ill patients. Higher APACHE II scores correlate with increased mortality, justifying its use as a reference in this study.12 PRDX1 demonstrated robust predictive performance (AUC=0.776, p<0.0001), comparable to the APACHE II score (AUC=0.778, p<0.0001). Although the combination of PRDX1 and APACHE II resulted in a higher AUC value (AUC=0.83, p<0.0001), indicating a potential trend towards improved predictive performance, statistical comparisons revealed no significant difference compared with either single indicator (p>0.05) (online supplemental table S4, figure 3C).
Figure 3. Circulating PRDX1 levels can serve as a prognostic biomarker for ARDS patients. (A) Effect of PRDX1 on OR for 28-day mortality. Age, gender, PCT, SCr, Pao2/Fio2, SOFA, APACHE II were adjusted. (B) Comparative serum PRDX1 levels between survival and death ARDS patients in the training cohort. (C) ROC curve analysis assessing the predictive value of APACHE II score, serum PRDX1 levels, and their combination for 28-day mortality in ARDS patients from the training cohort (n=90). (D) Comparative serum PRDX1 levels between survival and death ARDS patients in the validation cohort. (E) ROC curve analysis evaluating the predictive value of APACHE II score, serum PRDX1 levels and their combination for 28-day mortality in ARDS patients in the validation cohort (n=20). APACHE II, Acute Physiology and Chronic Health Evaluation; ARDS, acute respiratory distress syndrome; AUC, area under the curve; ROC, receiver operating characteristic; SOFA, Sequential Organ Failure Assessment.
To validate these findings, we recruited an independent cohort of 20 ARDS patients from the intensive care unit (ICU) of Xiangya Hospital, with 28-day mortality follow-up. Demographic and clinical characteristics of the validation cohort are summarised (online supplemental table S5). Consistent with the training cohort, non-survivors exhibited significantly higher serum PRDX1 levels compared with survivors (figure 3D). Serum PRDX1 demonstrated strong predictive capability for 28-day mortality (AUC=0.781, p<0.03), with performance comparable to the APACHE II scores (AUC=0.729, p=0.08). Although the combination of PRDX1 and APACHE II resulted in a higher AUC value (AUC=0.83, p=0.01), statistical comparisons revealed no significant difference compared with either single indicator (p>0.05) (online supplemental table S6, figure 3E).
Prdx1 levels elevate in experimental acute lung injury models
We investigated the relationship between acute lung injury (ALI) and serum Prdx1 levels in animal models. We established an LPS-induced ALI mouse model via intratracheal instillation. Histopathological analysis revealed time-dependent inflammatory cell infiltration, alveolar septal thickening and structural disruption in lung tissues. Concurrently, serum Prdx1 levels exhibited a marked elevation correlating with the progression of lung injury, demonstrating a strong positive correlation with the severity of pulmonary tissue damage (figure 4A–C).
Figure 4. Temporal dynamics of Prdx1 in ALI model induced by intratracheal LPS instillation. LPS (5 mg/kg) was administered via intratracheal instillation. (A) Representative H&E-stained lung sections (10×:scale bar=1000 µm; 200×:scale bar=50 µm). (B) Semiquantitative lung injury scores. (C) Serum Prdx1 levels. ALI, acute lung injury; LPS, lipopolysaccharide.
Subsequently, we developed a sepsis-associated ALI model through intraperitoneal LPS injection, which similarly manifested time-dependent histopathological alterations in lung tissues. Serum Prdx1 levels exhibited a significant increase concomitant with lung injury progression. Compared with the ALI model induced by intratracheal LPS instillation, we noted a more rapid elevation and higher peak concentrations of serum Prdx1 in the sepsis-associated ALI model (figure 5A–C).
Figure 5. Prdx1 levels were significantly elevated in the serum of LPS-induced sepsis-associated ALI mice. The sepsis-associated ALI model was established via intraperitoneal injection of LPS (10 mg/kg). (A) Representative H&E-stained lung sections (10×: scale bar=1000 µm; 200×: scale bar=50 µm). (B) Semiquantitative lung injury scores. (C) Serum Prdx1 levels. ALI, acute lung injury; LPS, lipopolysaccharide; ns, not significant.
These findings collectively suggest that serum Prdx1 levels exhibit a strong correlation with ALI and demonstrate more pronounced elevation in the presence of concomitant organ injury, highlighting its potential clinical utility in the management of critically ill patients.
Discussion
Our study is the first to reveal the role of circulating PRDX1 in ARDS patients. Elevated circulating PRDX1 serves as a biomarker of disease severity or multiorgan injury in ARDS patients and is significantly correlated with 28-day mortality. Furthermore, circulating PRDX1 exhibits strong prognostic predictive performance comparable to the widely used APACHE II score. The combination of PRDX1 and APACHE II resulted in an increased AUC value; however, no statistically significant difference was observed compared with either individual indicator. This numerical improvement suggests the potential value of multimarker integration, yet its definitive advantage requires further validation in larger-scale studies. In summary, these findings indicate that circulating PRDX1 can provide valuable prognostic information for ARDS patients and may serve as an important component in the ARDS management framework.
Despite multiple revisions to ARDS diagnostic criteria, misdiagnosis and underdiagnosis remain prevalent in clinical practice, a challenge rooted in ARDS’s clinical heterogeneity.4 13 This underscores the urgent need for highly specific diagnostic standards, necessitating deeper exploration of ARDS pathogenesis. Disruption of the alveolar epithelial-endothelial barrier and dysregulated inflammatory responses represents core pathophysiological processes driving ARDS progression.14 Biomarkers provide critical insights into these mechanisms. The receptor for advanced glycation end products (RAGE), highly expressed in alveolar epithelial cells, demonstrates elevated plasma soluble RAGE (sRAGE) levels in ARDS patients, correlating with lung injury severity and impaired alveolar fluid clearance.15 16 Plasma angiopoietin-2 (Ang-2) and von Willebrand factor, markers of endothelial injury, exhibit diagnostic value for ARDS. Additionally, pro-inflammatory cytokines such as IL-6 and IL-8 have been proposed as diagnostic references.7 Metabolomics has further elucidated pathophysiological dynamics in ARDS development. A metabolomic analysis of BALF from ARDS patients with varying severity identified metabolites such as taurine, arginine and threonine that effectively differentiated disease severity.17 However, the clinical heterogeneity of ARDS complicates biomarker utility: distinct biomarkers may demonstrate preferential associations with specific aetiologies, facilitating subphenotype identification while limiting broad applicability. For instance, ARDS triggered by direct pulmonary insults (eg, pneumonia) is characterised by heightened epithelial injury (elevated plasma sRAGE and SP-D), whereas indirect aetiologies (eg, sepsis) exhibit distinct biomarker profiles.18
The widespread expression of PRDX1 in lung tissue and its injury-induced secretion pattern support its potential as a diagnostic biomarker for ARDS. Nevertheless, our current study data do not support circulating PRDX1 serving as a diagnostic biomarker for ARDS. This is based on two key findings. First, in the challenging differential diagnoses relevant to ARDS and critical care management, circulating PRDX1 cannot effectively distinguish ARDS from conditions such as cardiogenic pulmonary oedema, atelectasis and pleural effusion. Second, circulating PRDX1 levels are significantly higher in ARDS patients complicated with multi-organ failure. This contribution from extra-pulmonary organ injury substantially limits the efficacy and clinical applicability of PRDX1 as a specific diagnostic biomarker for ARDS. Consequently, when interpreting the diagnostic utility of circulating PRDX1 within these two clinical contexts, our results do not support its use as an ARDS-specific diagnostic biomarker.
Despite advancements in respiratory support, ARDS mortality remains high (>40%), with our study reporting a 28-day mortality rate of 48.9%, highlighting unmet needs in ARDS management. Current research underscores the prognostic potential of biomarkers in ARDS. For example, elevated plasma levels of sRAGE independently predict 28 and 90-day mortality in ARDS patients.19 20 Studies have classified ARDS into hypoinflammatory and hyperinflammatory subphenotypes, with the hyperinflammatory subtype exhibiting twice the 90-day mortality of the hypoinflammatory subtype.21 Notably, inflammatory subphenotyping may guide therapeutic strategies, as hyperinflammatory patients may benefit from higher positive end-expiratory pressure levels.6 Supporting this, a transcriptomic study of ARDS and sepsis patients indicated that the hyperinflammatory subphenotype exhibits enhanced expression of innate immune and metabolic genes alongside increased abundance of bacterial DNA in the blood. In contrast, the hypoinflammatory subphenotype is marked by T cell signalling, suggesting immunosuppression and metabolic dysfunction.22 In our study, serum PRDX1 demonstrated positive correlations with inflammatory markers (IL-6, MCP-1, TNF-α) and disease severity scores (SOFA, APACHE II), suggesting its ability to reflect systemic inflammatory phenotypes and disease severity. This positions PRDX1 as a potentially valuable tool for prognostic stratification. Specifically, the robust ability of PRDX1—especially when combined with APACHE II—to identify patients at the highest risk of mortality could be leveraged for early triage. For example, elevated PRDX1 levels on ICU admission could flag patients warranting more intensive monitoring or with whom goals of care should be proactively discussed. Moreover, the strong positive correlations between circulating PRDX1 and canonical inflammatory mediators suggest it may serve as a clinically tractable proxy for identifying the deleterious hyperinflammatory subphenotype. This could potentially guide the application of immunomodulatory agents in ARDS patients. Further clinical and experimental investigations are required to definitively establish the relationship of circulating PRDX1 with various disease subphenotypes and to validate its clinical application.
Recent preclinical studies investigating circulating PRDX1 in acute organ injuries have elucidated the role of extracellular PRDX1. Current evidence indicates that circulating PRDX1 levels are significantly elevated during acute brain, liver and kidney injuries.8,10 Following parenchymal cell damage, intracellular Prdx1 is secreted into the extracellular space, where it functions as a DAMP. By binding PRRs such as TLR2/4 and Mincle, extracellular Prdx1 activates innate immunity, amplifies inflammatory responses and exacerbates organ damage.8 9 Notably, Prdx1-specific monoclonal antibodies have demonstrated promising therapeutic efficacy in animal models of acute liver and kidney injury. In the context of ALI, proteomic analysis of lung tissues from Pseudomonas aeruginosa-induced ALI rats revealed significant upregulation of Prdx1 expression.23 Additionally, studies have demonstrated that ferulic acid alleviates LPS-induced ALI in mice by covalently binding to Prdx1, inhibiting its dimerisation and secretion, thereby modulating the Prdx1/TLR4 signalling pathway.24 Collectively, these findings indicate that Prdx1 plays a crucial pro-inflammatory role in the pathogenesis and progression of ALI, suggesting its potential as a therapeutic target for ALI/ARDS intervention. However, further investigations are required to validate these observations and explore translational applications.
Additionally, we observed higher serum PRDX1 levels in ARDS patients with multiorgan injuries. Clinically, ARDS patients are typically older and prone to comorbidities involving other organ systems, which are associated with adverse outcomes. Given the ubiquitous expression of PRDX1 and its injury-mediated release, circulating PRDX1 levels are theoretically elevated in ARDS patients with multiorgan/system injuries. This hypothesis was confirmed in our study: ARDS patients with ≥3 organ/system involvements exhibited significantly higher circulating PRDX1 levels compared with those with isolated pulmonary injury. These findings were further validated in animal models. Sepsis-associated ALI mice demonstrated earlier elevation and higher abundance of serum Prdx1 compared with ALI models induced by intratracheal LPS instillation. These results emphasise its translational potential for clinical stratification and management.
Our study has several limitations. First, the relatively small sample size raises concerns about the generalisability of the findings, necessitating validation in a larger multicentre RICU cohort. Second, the practical implications of circulating PRDX1 for clinical management in ARDS patients remain unclear; its potential value for subphenotyping or guiding treatment decisions requires further investigation. Additionally, biomarkers should ideally monitor lung injury progression/repair and therapeutic responses in ARDS. We only collected blood samples within 24 hours of ARDS diagnosis and did not track subsequent therapeutic responses or perform multi-timepoint measurements of circulating PRDX1 levels. Future studies should focus on its pharmacokinetics in humans and correlations with therapeutic responses.
In conclusion, serum PRDX1 is significantly elevated in ARDS patients and demonstrates strong prognostic performance, offering a novel biomarker with substantial translational potential for clinical stratification and management.
Supplementary material
Footnotes
Funding: This research was financially supported by the National Natural Science Foundation of China, enabling our investigation into this critical field (Grant No. 82270079 and 82300096).
Provenance and peer review: Not commissioned; externally peer reviewed.
Patient consent for publication: Not applicable.
Ethics approval: This study involves human participants and was approved by the Ethics Committee of Third Xiangya Hospital (Approval No. K25464) and Xiangya Hospital (Approval No.2025050935). Participants gave informed consent to participate in the study before taking part.
Patient and public involvement: Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Data availability statement
Data are available on reasonable request.
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Data Availability Statement
Data are available on reasonable request.