Role of Sulfur Dioxide in Acute Lung Injury Following Limb Ischemia/Reperfusion in Rats

A near-infrared lysosomal probe for dynamic sulfur dioxide monitoring in inflammation

Inflammation is a complex physiological response involving various cellular and molecular events. Sulfur dioxide (SO2), recognized as both an endogenous signaling molecule and anti-inflammatory agent, plays a crucial role in modulating inflammation and maintaining cellular homeostasis. To gain deeper insights into the dynamics of inflammation-related processes, real-time monitoring of SO2 concentrations within cellular organelles is imperative. Here, we developed a near-infrared fluorescent probe, R2, equipped with lysosomal targeting features. R2 effectively monitors dynamic SO2 concentration changes during inflammation. The fluorescence intensity at 703 nm of R2 shows a strong linear correlation with the concentration of SO2, displaying a rapid response time to SO2 within 10 s and maintaining excellent photostability. The successful application of R2 in elucidating dynamic SO2 concentration changes in lysosomal during cellular and rat inflammatory processes underscores its significant potential as a tool for understanding the pathogenesis of inflammation-related diseases.

Unveiling the Potential of Sulfur-Containing Gas Signaling Molecules in Acute Lung Injury: A Promising Therapeutic Avenue

Acute lung injury (ALI) and its most severe form, acute respiratory distress syndrome (ARDS), are pulmonary conditions that cause significant morbidity and mortality. The common etiologies of these conditions include pneumonia, pulmonary contusion, fat embolism, smoke inhalation, sepsis, shock, and acute pancreatitis. Inflammation, oxidative stress, apoptosis, and autophagy are key pathophysiological mechanisms underlying ALI. Hydrogen sulfide (H2S) and sulfur dioxide (SO2) are sulfur-containing gas signaling molecules that can mitigate these pathogenic processes by modulating various signaling pathways, such as toll-like receptor 4 (TLR4)/nod-like receptor protein 3 (NLRP3), extracellular signal-regulating protein kinase 1/2 (ERK1/2), mitogen-activated protein kinase (MAPK), phosphatidyl inositol 3 kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR), and nuclear factor kappa B (NF-κB), thereby conferring protection against ALI. Given the limited clinical effectiveness of prevailing ALI treatments, investigation of the modulation of sulfur-containing gas signaling molecules (H2S and SO2) in ALI is imperative. This article presents an overview of the regulatory pathways of sulfur-containing gas signaling molecules in ALI animal models induced by various stimuli, such as lipopolysaccharide, gas inhalation, oleic acid, and ischemia-reperfusion. Furthermore, this study explored the therapeutic prospects of diverse H2S and SO2 donors for ALI, stemming from diverse etiologies. The aim of the present study was to establish a theoretical framework, in order to promote the new treatment of ALI.

Rational Construction of a Mitochondria-Targeted Reversible Fluorescent Probe with Intramolecular FRET for Ratiometric Monitoring Sulfur Dioxide and Formaldehyde

Sulfur dioxide (SO₂) and formaldehyde (FA) are important species that maintain redox homeostasis in life and are closely related to many physiological and pathological processes. Therefore, it is of great significance to realize the reversible monitoring of them at the intracellular level. Here, we synthesized a reversible ratiometric fluorescent probe through a reasonable design, which can sensitively monitor SO₂ derivatives and FA, and the detection limit can reach 0.16 μM. The probe can specifically target mitochondria and successfully monitor the fluctuations of SO₂ and FA in living cells. It also works well in the detection of SO₂ and FA in zebrafish. This high-performance probe is expected to find broad in vitro and in vivo applications.

Sulfur Dioxide: Endogenous Generation, Biological Effects, Detection, and Therapeutic Potential

Significance: Previously, sulfur dioxide (SO₂) was recognized as an air pollutant. However, it is found to be endogenously produced in mammalian tissues. As a new gasotransmitter, SO₂ is involved in regulating the structure and function of blood vessels, heart, lung, gastrointestinal tract, nervous system, etc.Recent Advances: Increasing evidence showed that endogenous SO₂ regulates cardiovascular physiological processes, such as blood pressure control, vasodilation, maintenance of the normal vascular structure, and cardiac negative inotropy. Under pathological conditions including hypertension, atherosclerosis, vascular calcification, aging endothelial dysfunction, myocardial injury, myocardial hypertrophy, diabetic myocardial fibrosis, sepsis-induced cardiac dysfunction, pulmonary hypertension, acute lung injury, colitis, epilepsy-related brain injury, depression and anxiety, and addictive drug reward memory consolidation, endogenous SO₂ protects against the pathological changes via different molecular mechanisms and the disturbed SO₂/aspartate aminotransferase pathway is likely involved in the mechanisms for the earlier mentioned pathologic processes. Critical Issues: A comprehensive understanding of the biological effects of endogenous SO₂ is extremely important for the development of novel SO₂ therapy. In this review, we summarized the biological effects, mechanism of action, SO₂ detection methods, and its related prodrugs. Future Directions: Further studies should be conducted to understand the effects of endogenous SO₂ in various physiological and pathophysiological processes and clarify its underlying mechanisms. More efficient and accurate SO₂ detection methods, as well as specific and effective SO₂-releasing systems should be designed for the treatment and prevention of clinical related diseases. The translation from SO₂ basic medical research to its clinical application is also worthy of further study. Antioxid. Redox Signal. 36, 256-274.

Macrophage-derived sulfur dioxide is a novel inflammation regulator

Macrophage-mediated inflammation is a key pathophysiological component of cardiovascular diseases, but the underlying mechanisms by which the macrophage regulates inflammation have been unclear. In our study, we, for the first time, showed an endogenous sulfur dioxide (SO₂) production in RAW267.4 macrophages by using HPLC and SO₂-specific fluorescent probe assays. Moreover, the endogenous SO₂ generating enzyme aspartate aminotransferase (AAT) was found to be expressed by the macrophages. Furthermore, we showed that AAT2 knockdown triggered spontaneous macrophage-mediated inflammation, as represented by the increased TNF-α and IL-6 levels and the enhanced macrophage chemotaxis; these effects could be reversed by the treatment with a SO₂ donor. Mechanistically, AAT2 knockdown activated the NF-κB signaling pathway in macrophages, while SO₂ successfully rescued NF-κB activation. In contrast, forced AAT2 expression reversed AngII-induced NF-κB activation and subsequent macrophage inflammation. Moreover, treatment with a SO₂ donor also alleviated macrophage infiltration in AngII-treated mouse hearts. Collectively, our data suggest that macrophage-derived SO₂ is an important regulator of macrophage activation and it acts as an endogenous "on-off switch" in the control of macrophage activation. This knowledge might enable a new therapeutic strategy for cardiovascular diseases.

Impacts of air pollution wave on years of life lost: A crucial way to communicate the health risks of air pollution to the public

Limited studies have explored the impacts of exposure to sustained high levels of air pollution (air pollution wave) on mortality. Given that the frequency, intensity and duration of air pollution wave has been increasing in highly polluted regions recently, understanding the impacts of air pollution wave is crucial. In this study, air pollution wave was defined as 2 or more consecutive days with air pollution index (API) > 100. The impacts of air pollution wave on years of life lost (YLL) due to non-accidental, cardiovascular and respiratory deaths were evaluated by considering both consecutive days with high levels of air pollution and daily air pollution levels in Tianjin, China, from 2006 to 2011. The results showed the durational effect of consecutive days with high levels of air pollution was substantial in addition to the effect of daily air pollution. For instance, the durational effect was related to an increase in YLL of 116.6 (95% CI: 4.8, 228.5) years from non-accidental deaths when the air pollution wave was sustained for 4 days, while the corresponding daily air pollution's effect was 121.2 (95% CI: 55.2, 187.1) years. A better interpretation of the health risks of air pollution wave is crucial for air pollution control policy making and public health interventions.

Role of carbonyl sulfide in acute lung injury following limb ischemia/reperfusion in rats

OBJECTIVE

To investigate the effect of carbonyl sulfide (COS) on limb ischemia/reperfusion (I/R)-induced acute lung injury (ALI) and the associated mechanism in rats.

METHODS

ALI was induced by bilateral hind limb I/R in Sprague-Dawley (SD) rats. Sixty-four SD rats were randomly divided into the control group, I/R group, I/R + COS group, and I/R + AIR group. We observed the survival rate of the rats and the morphological changes of lung tissues, and we measured the change in the lung coefficient, the expression levels of the intercellular adhesion factor-1 (ICAM-1) protein in lung tissue, the expression of tumor necrosis factor (TNF)-α, interleukin (IL)-lβ, and interleukin (IL)-6 in both lung tissue and serum, and cell apoptosis.

RESULTS

Limb I/R caused significant lung tissue damage. The number of polymorphonuclear neutrophil in alveolar septa, the expression level of the ICAM-1 protein in lung tissue, the expression levels of TNF-α, IL-1, and IL-6 in lung tissue and serum, the lung coefficient, and cell apoptosis all increased. When a low dose of COS gas was administered prior to limb I/R, the variation of the above indicators was significantly reduced, while an increase in the dose of COS did not reduce the lung injury but rather increased the mortality rate.

CONCLUSION

Carbonyl sulfide is another new gaseous signaling molecule, and a low dose of exogenous COS may play a protective role in I/R-induced ALI by acting as an anti-inflammatory agent by promoting the production of antioxidants and by inhibiting the expression of adhesion molecule proteins.

Endogenous sulfur dioxide is a novel adipocyte-derived inflammatory inhibitor

The present study was designed to determine whether sulfur dioxide (SO₂) could be endogenously produced in adipocyte and served as a novel adipocyte-derived inflammatory inhibitor. SO₂ was detected in adipose tissue using high-performance liquid chromatography with fluorescence detection. SO₂ synthase aspartate aminotransferase (AAT1 and AAT2) mRNA and protein expressions in adipose tissues were measured. For in vitro study, 3T3-L1 adipocytes were cultured, infected with adenovirus carrying AAT1 gene or lentivirus carrying shRNA to AAT1, and then treated with tumor necrosis factor-α (TNF-α). We found that endogenous SO₂/AAT pathway existed in adipose tissues including perivascular, perirenal, epididymal, subcutaneous and brown adipose tissue. AAT1 overexpression significantly increased SO₂ production and inhibited TNF-α-induced inflammatory factors, monocyte chemoattractant protein-1 (MCP-1) and interleukin-8 (IL-8) secretion from 3T3-L1 adipocytes. By contrast, AAT1 knockdown decreased SO₂ production and exacerbated TNF-α-stimulated MCP-1 and IL-8 secretion. Mechanistically, AAT1 overexpression attenuated TNF-α-induced IκBα phosphorylation and degradation, and nuclear factor-κB (NF-κB) p65 phosphorylation, while AAT1 knockdown aggravated TNF-α-activated NF-κB pathway, which was blocked by SO₂. NF-κB inhibitors, PDTC or Bay 11-7082, abolished excessive p65 phosphorylation and adipocyte inflammation induced by AAT1 knockdown. This is the first report to suggest that endogenous SO₂ is a novel adipocyte-derived inflammatory inhibitor.

The PI3K/Akt, p38MAPK, and JAK2/STAT3 signaling pathways mediate the protection of SO2 against acute lung injury induced by limb ischemia/reperfusion in rats

Sulfur dioxide (SO2) is naturally synthesized by glutamate-oxaloacetate transaminase (GOT) from L-cysteine in mammalian cells. We found that SO2 may have a protective effect on acute lung injury (ALI) induced by limb ischemia/reperfusion (I/R) in rats. The PI3K/Akt, p38MAPK, and JAK2/STAT3 pathways are crucial in cell signaling transduction. The present study aims to verify the role of SO2 on limb I/R-induced ALI, and investigate whether PI3K/Akt, p38MAPK, and JAK2/STAT3 pathways were involved, as well as the relationship among the three pathways; we used specific inhibitors (LY294002, SB03580, and Stattic) to block them, respectively. The experimental methods of Western, ELISA, TUNEL, etc., were used to test the results. In the I/R group, the parameters of lung injury (MDA, MPO, TUNEL, cytokines) increased significantly, but the administration of Na2SO3/NaHSO3 attenuated the damage in the lung. The Western results showed that the rat's lung exist expression of P-STAT3, P-AKT, and P-p38 proteins. After I/R, P-STAT3, P-Akt, and P-p38 proteins expression all increased. After using Na2SO3/NaHSO3, P-Akt, and P-p38 proteins expression increased, but P-STAT3 protein expression decreased. We also found a strange phenomenon; compared to the I/R + SO2 group, the administration of stattic, P-p38 protein expression showed no change, but P-Akt protein expression increased (p < 0.05). In conclusion, SO2 has a protective effect on rats with limb I/R-induced ALI. The JAK2/STAT3, PI3K/Akt, and p38MAPK pathways are likely all involved in the process, and the JAK2/STAT3 pathway may have an impact on the P13K/Akt pathway.

The significance and mechanism of propofol on treatment of ischemia reperfusion induced lung injury in rats

This study is aimed to investigate the efficacy and underlying the mechanism of propofol in treatment of ischemia reperfusion (IR)-induced lung injury in rats, providing a novel insight of therapeutic strategy for IR-induced lung injury. 120 healthy SD rats were selected and randomly divided into sham operation group, IR group, and propofol group (40 rats per group). Bronchoalveolar lavage fluid (BALF) protein content, serum protein content, lung permeability index, lung water content rate, methane dicarboxylic aldehyde (MDA) in lung tissue, superoxide dismutase (SOD), nitric oxide (NO), endothelin (ET-1), toll-like receptor 4 (TLR4), nuclear factor (NF-κB), and tumor necrosis factor-α (TNF-α) were examined and compared among different groups to evaluate the therapeutical effects of propofol on IR-induced lung injury and analyze the mechanism. In sham operation group, neither change in lung tissue nor pulmonary interstitial edema or alveolar wall damage was found under microscope; in IR group, marked pulmonary interstitial edema and alveolar wall damage complicated with inflammatory cell infiltration and hemorrhage were found; in propofol group, alveolar wall widening was observed, however, hemorrhage in alveolar cavity, inflammatory infiltration and tissue damage were less significant than in IR group. At 3 h after reperfusion, BALF protein content, lung permeability index, and lung water content rate were all significantly increased in IR group and propofol group, while the serum protein content was significantly lower than sham operation group (p < 0.05). Moreover, we found that the change of above parameters in propofol group was less significant than in IR group (p < 0.05). No statistically significant difference was found in ET-1 levels in different groups (p > 0.05). In contrast, MDA and NO in IR group and propofol group were significantly increased, while SOD activity was significantly decreased (p < 0.05). Furthermore, the change of above parameters in propofol group was less significant than in IR group (p < 0.05). In addition, mRNAs of TLR4, NF-κB, and TNF-α were significantly increased in IR group and propofol group (p < 0.05) with more significant change in IR group compared with propofol group (p < 0.05). Propofol has protective effects against IR-induced lung injury by improving activity of oxygen radical and restoring NO/ET-1 dynamic balance. Besides, regulation of TLR4, NF-κB, and TNF-α by propofol also play important role in alleviating IR-induced lung injury.