Plasma Endogenous Sulfur Dioxide: A Novel Biomarker to Predict Acute Kidney Injury in Critically Ill Patients

A Kidney-Targeted Rapid Photoacoustic Probe Activated by Sulfur Dioxide for 3D Visual Diagnosis of Iodinated Contrast-Induced Acute Kidney Injury

Sulfur dioxide (SO2) dysmetabolism is closely associated with various diseases such as acute kidney injury (AKI). Nevertheless, the relationship between SO2 levels and iodinated contrast-induced AKI remains largely unclear. Therefore, accurate imaging of SO2 level fluctuations in vivo is therefore critically important. However, no photoacoustic (PA) imaging method is currently available for the detection of SO2. To address this gap, we designed and synthesized a PA probe toward SO2, namely, Rho-QL, for the first time and performed in situ PA imaging of SO2 in deep tissues in vivo. A novel method was accordingly developed for the 3D visual diagnosis of AKI based on PA imaging of SO2 in kidney tissues with high spatial resolution. Rho-QL exhibited a PA response time of 5 s for SO2 and displayed remarkable turn-on absorption changes at 700 nm, making it a suitable probe for detecting SO2 levels via PA imaging. Moreover, Rho-QL exhibited an excellent targeting ability to the kidney, thereby facilitating in situ imaging of SO2 in the kidney. Notably, through real-time PA imaging, Rho-QL was successfully applied for 3D visualization of the detailed SO2 distribution with high spatial resolution and revealed a remarkable increase in the SO2 levels in the kidney during a contrast-induced AKI process. Based on the current findings, Rho-QL is expected to become a powerful tool for the study and diagnosis of AKI-related diseases.

Sulfur Dioxide Alleviates Organ Damage and Inflammatory Response in Cecal Ligation and Puncture-Induced Sepsis Rat

The study aimed to elucidate the mechanisms by which sulfur dioxide (SO2) alleviates organ damage during sepsis using RNA-Seq technology. A cecal ligation and puncture (CLP) sepsis model was established in rats, and the effects of SO2 treatment on organ damage were assessed through histopathological examinations. RNA-Seq was performed to analyze differentially expressed genes (DEGs), and subsequent functional annotations and enrichment analyses were conducted. The CLP model successfully induced sepsis symptoms in rats. Histopathological evaluation revealed that SO2 treatment considerably reduced tissue damage across the heart, kidney, liver, and lungs. RNA-Seq identified 950 DEGs between treated and untreated groups, with significant enrichment in genes associated with ribosomal and translational activities, amino acid metabolism, and PI3K-Akt signaling. Furthermore, gene set enrichment analysis (GSEA) showcased enrichments in pathways related to transcriptional regulation, cellular migration, proliferation, and calcium-ion binding. In conclusion, SO2 effectively mitigates multi-organ damage induced by CLP sepsis, potentially through modulating gene expression patterns related to critical biological processes and signaling pathways. These findings highlight the therapeutic promise of SO2 in managing sepsis-induced organ damage.

Benzylic rearrangement for urinary analysis of guanidino and ureido compounds in cardiac surgery-associated acute kidney injury using high-performance liquid chromatography-tandem mass spectrometry

Rationale

Because acute kidney injury (AKI) is closely related to poor prognosis in critically ill patients, developing biomarkers for its prediction and early diagnosis is particularly important. Endogenous guanidino compounds (GCs) and ureido compounds (UCs) can participate in various biochemical processes because of their important physiological activities. The aim of this study was to investigate the alteration profiles of urinary GCs/UCs as potential biomarkers in patients with cardiac surgery–associated acute kidney injury (CSA‐AKI) at different stages.

Methods

GCs/UCs were reacted with benzil via benzylic rearrangement, and their derivatives were used to investigate fragmentation mechanisms using tandem mass spectrometry (MS/MS) in positive ion mode. Furthermore, a high‐performance liquid chromatography (HPLC)–MS/MS method was developed to measure the concentrations of GCs/UCs in urine samples taken from patients with CSA‐AKI at different time points.

Results

MS/MS analysis in positive ion mode showed that benzylic GCs/UCs exhibited similar fragmentation processes, which could produce the characteristic ion (C13H12N+) at m/z 182.0. Furthermore, an obviously different fragmentation pattern of benzylic UCs in the positive ion mode might be due to the neutral loss of the H2CO2 group under low collision energy. Of the eight selected GCs/UCs, methylguanidine exhibited significantly increased concentrations in urine when CSA‐AKI occurred, whereas guanidinoethyl sulfonate (GDS), homoarginine (HArg) and homocitrulline (HCit) exhibited decreased concentrations. After recovery from AKI, the urinary concentrations of the aforementioned GCs/UCs returned to normal. Some of the aforementioned metabolites with significant changes (GDS, HArg and HCit) had large areas under the curve in the receiver operating characteristic curve for distinguishing AKI stages on the third day after surgery.

Conclusions

In patients with CSA‐AKI, urinary GCs/UCs were significantly disrupted due to injured kidney, and some GC/UC metabolites exhibited a good ability to become potential biomarkers for AKI stages. The present study provides essential resources and new therapeutic targets for further research on CSA‐AKI.

Kidney-Targeted Near-Infrared Fluorescence Probe Reveals That SO2 Is a Biomarker for Cisplatin-Induced Acute Kidney Injury

With the widespread use of drugs, drug-induced acute kidney injury (AKI) has become an increasingly serious health concern worldwide. Currently, early diagnosis of drug-induced AKI remains challenging because of the lack of effective biomarkers and noninvasive imaging tools. SO2 plays important physiological roles in living systems and is an important antioxidant for maintaining redox homeostasis. However, the relationship between SO2 (in water as SO32-/HSO3-) and drug-induced AKI remains largely unknown. Herein, we report the highly sensitive near-infrared fluorescence probe DSMN, which for the first time reveals the relationship between SO2 and drug-induced AKI. The probe responds to SO32-/HSO3- selectively and rapidly (within seconds) and shows a significant turn-on fluorescence at 710 nm with a large Stokes shift (125 nm). With these properties, the probe was successfully applied to detect SO2 in living cells and mice. Importantly, the probe can selectively target the kidneys, allowing for the detection of changes in the SO2 concentration in the kidneys. Based on this, DSMN was successfully used to detect cisplatin-induced AKI and revealed an increase in the SO2 levels. The results indicate that SO2 is a new biomarker for AKI and that DSMN is a powerful tool for studying and diagnosing drug-induced AKI.

Association between ambient air pollutant interaction with kidney function in a large Taiwanese population study

The associations and interactions between kidney function and other air pollutants remain poorly defined. Therefore, the aim of this study was to evaluate associations among air pollutants, including particulate matter (PM) with a diameter ≤ 2.5 μm (PM2.5), PM10 (PM with a diameter ≤ 10 μm), carbon monoxide (CO), nitrogen oxide (NO), nitrogen oxides (NOx), sulfur dioxide (SO2), and ozone (O3) with kidney function, and explore interactions among these air pollutants on kidney function. We used the Taiwan Air Quality Monitoring and Taiwan Biobank databases to derive data on community-dwelling individuals in Taiwan and daily air pollution levels, respectively. We enrolled 26,032 participants. Multivariable analysis showed that high levels of PM2.5, PM10, O3 (all p < 0.001), and SO2 (p = 0.001) and low levels of CO, NO (both p < 0.001), and NOx (p = 0.047) were significantly correlated with low estimated glomerular filtration rate (eGFR). With regard to negative effects, the interactions between PM2.5 and PM10 (p < 0.001), PM2.5 and PM10 (p < 0.001), PM2.5 and SO2, PM10 and O3 (both p = 0.025), PM10 and SO2 (p = 0.001), and O3 and SO2 (p < 0.001) on eGFR were significantly negatively. High PM10, PM2.5, O3, and SO2 were associated with a low eGFR, whereas high CO, NO, and NOx were associated with a high eGFR. Furthermore, negative interactions between PM2.5 and PM10, O3 and SO2, PM10 and O3, PM2.5 and SO2, and PM10 and SO2 on eGFR were observed. The findings of this study have important implications for public health and environmental policy. Specifically, the results of this study may be useful in individuals and organizations to take action to reduce air pollution and promote public health.

Endogenous SO2 Controls Cell Apoptosis: The State-of-the-Art

SO2, previously known as the product of industrial waste, has recently been proven to be a novel gasotransmitter in the cardiovascular system. It is endogenously produced from the metabolism pathway of sulfur-containing amino acids in mammalians. Endogenous SO2 acts as an important controller in the regulation of many biological processes including cardiovascular physiological and pathophysiological events. Recently, the studies on the regulatory effect of endogenous SO2 on cell apoptosis and its pathophysiological significance have attracted great attention. Endogenous SO2 can regulate the apoptosis of vascular smooth muscle cells, endothelial cells, cardiomyocytes, neuron, alveolar macrophages, polymorphonuclear neutrophils and retinal photoreceptor cells, which might be involved in the pathogenesis of hypertension, pulmonary hypertension, myocardial injury, brain injury, acute lung injury, and retinal disease. Therefore, in the present study, we described the current findings on how endogenous SO2 is generated and metabolized, and we summarized its regulatory effects on cell apoptosis, underlying mechanisms, and pathophysiological relevance.