Effect of sulfur dioxide preconditioning on rat myocardial ischemia/reperfusion injury by inducing endoplasmic reticulum stress

Rapid and on-site detection of bisulfite via a NIR fluorescent probe: A case study on the emission wavelength of probes with different quinolinium as electron-withdrawing groups

The emission of venenous sulfur dioxide (SO2) and its derivatives from industrial applications such as coking, transportation and food processing has caused great concern about public health and environmental quality. Probes that enable sensitivity and specificity to detect SO2 derivatives play a crucial role in its regulations and finally mitigating its environmental and health impacts, but fluorescent probes that can accurately, rapidly and on-site detect SO2 derivatives in foodstuffs and environmental systems rarely reported. Herein, a near-infrared (NIR) fluorescent probe (ZTX) for the ratiometric response of bisulfite (HSO3-) was designed and synthesized by regulating the structure of high-performance HSO3- fluorescent probe SL previously reported by us based on structural analyses, theoretical calculations and related literature reports. The Michael addition reaction between the electronic-deficient C=C bond and HSO3- destroys ZTX's π-conjugation system and blocks its intramolecular charge transfer (ICT) process, resulting in a significant fading of the fuchsia solution and the bluish-purple fluorescence turned light blue fluorescence. Fluorescent imaging of HSO3- in live animals utilizing ZTX has been demonstrated. The quantitative analysis of HSO3- in food samples using ZTXvia a smartphone has been also successfully implemented. Simultaneously, the ZTX-based test strips were utilized to quantificationally determine HSO3- in environmental water samples by a smartphone. Consequently, probe ZTX could provide a new method to understand the physiopathological roles of HSO3-, evaluate food safety and monitor environment, and is promising for broad applications.

Color-reversible fluorescence tracking for the dynamic interaction of SO2 with Hg2+ in living cells

Mercury ion (Hg2+) is one of the most threatening substances to human health, and the mercury poisoning can damage physiological homeostasis severely in human, even cause death. Intriguingly, Sulfur dioxide (SO2), a gas signal molecule in human, can specifically interact with Hg2+ for relieving mercury poisoning. However, the dynamic interaction of Hg2+ with SO2 at the tempospatial level and the correlation between Hg2+ and SO2 in the pathological process of mercury poisoning are still elusive. Herein, we rationally designed a reversible and dual color fluorescent probe (CCS) for dynamically visualizing Hg2+ and SO2 and deciphering their interrelationship in mercury poisoning. CCS held good sensitivity, selectivity and reversibility to Hg2+ and SO2, that enabled CCS to specifically detect SO2 and Hg2+ via cyan fluorescence channel (centered around 485 nm) and red fluorescence channel (centered around 679 nm), respectively. Notably, the separate fluorescence signal changes of CCS realized the dynamic tracing of Hg2+ and SO2 in living cells, and presented the potential for exploring the correlation between SO2 and Hg2+ in mercury poisoning.

Sulfur dioxide inhibits mast cell degranulation by sulphenylation of galectin-9 at cysteine 74

Objectives

Mast cell (MC) degranulation is a key process in allergic reactions and inflammatory responses. Aspartate aminotransferase 1 (AAT1)-derived endogenous sulfur dioxide (SO2) is an important regulator of MC function. However, the mechanism underlying its role in MC degranulation remains unclear. This study aimed to investigate the mechanism by which endogenous SO2 controlled MC degranulation.

Methods

HMC-1 and Rat basophilic leukemia cell MC line (RBL-2H3) were used in the cell experiments. SO2 content was detected by in situ fluorescent probe. MC degranulation represented by the release rate of MC β-hexosaminidase was determined using a colorimetric assay. Sulfenylation of galectin-9 (Gal-9) in MCs and purified protein was detected using a biotin switch assay. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine the exact sulfenylation sites of Gal-9 by SO2. Animal models of passive cutaneous anaphylaxis (PCA) and hypoxia-driven pulmonary vascular remodeling were used to investigate the effect of SO2 on mast cell activation in vivo. Site-directed mutation of Gal-9 was conducted to confirm the exact site of SO2 and support the significance of SO2/Gal-9 signal axis in the regulation of MC degranulation.

Results

Degranulation was increased in AAT1-knockdowned MCs, and SO2 supplementation reversed the increase in MC degranulation. Furthermore, deficiency of endogenous SO2 contributed to IgE-mediated degranulation in vitro. Besides, SO2 inhibited IgE-mediated and hypoxia-driven MC degranulation in vivo. Mechanistically, LC-MS/MS analysis and site-directed mutation results showed that SO2 sulfenylated Gal-9 at cysteine 74. Sulfenylation of the 74th cysteine of Gal-9 protein was required in the SO2-inhibited MC degranulation under both physiological and pathophysiological conditions.

Conclusion

These findings elucidated that SO2 inhibited MC degranulation via sulfenylating Gal-9 under both physiological and pathophysiological conditions, which might provide a novel treatment approach for MC activation-related diseases.

Endogenous sulfur dioxide deficiency as a driver of cardiomyocyte senescence through abolishing sulphenylation of STAT3 at cysteine 259

OBJECTIVE

Cardiomyocyte senescence is an important contributor to cardiovascular diseases and can be induced by stressors including DNA damage, oxidative stress, mitochondrial dysfunction, epigenetic regulation, etc. However, the underlying mechanisms for the development of cardiomyocyte senescence remain largely unknown. Sulfur dioxide (SO2) is produced endogenously by aspartate aminotransferase 2 (AAT2) catalysis and plays an important regulatory role in the development of cardiovascular diseases. The present study aimed to explore the effect of endogenous SO2 on cardiomyocyte senescence and the underlying molecular mechanisms.

APPROACH AND RESULTS

We interestingly found a substantial reduction in the expression of AAT2 in the heart of aged mice in comparison to young mice. AAT2-knockdowned cardiomyocytes exhibited reduced SO2 content, elevated expression levels of Tp53, p21Cip/Waf, and p16INk4a, enhanced SA-β-Gal activity, and elevated level of γ-H2AX foci. Notably, supplementation with a SO2 donor ameliorated the spontaneous senescence phenotype and DNA damage caused by AAT2 deficiency in cardiomyocytes. Mechanistically, AAT2 deficiency suppressed the sulphenylation of signal transducer and activator of transcription 3 (STAT3) facilitated its nuclear translocation and DNA-binding capacity. Conversely, a mutation in the cysteine (Cys) 259 residue of STAT3 blocked SO2-induced STAT3 sulphenylation and subsequently prevented the inhibitory effect of SO2 on STAT3-DNA-binding capacity, DNA damage, and cardiomyocyte senescence. Additionally, cardiomyocyte (cm)-specific AAT2 knockout (AAT2cmKO) mice exhibited a deterioration in cardiac function, cardiomegaly, and cardiac aging, whereas supplementation with SO2 donors mitigated the cardiac aging and remodeling phenotypes in AAT2cmKO mice.

CONCLUSION

Downregulation of the endogenous SO2/AAT2 pathway is a crucial pathogenic mechanism underlying cardiomyocyte senescence. Endogenous SO2 modifies STAT3 by sulphenylating Cys259, leading to the inhibition of DNA damage and the protection against cardiomyocyte senescence.

Differential evaluation of sulfur oxides in the natural lake water samples by carbazole-furan fluorescent probe

Water bodies are frequently polluted, with sulfur oxides being the most common form of water pollution. Therefore, developing a detection mechanism for sulfur oxides in water bodies is particularly urgent. A new fluorescent probe YX-KZBD was designed and developed. This probe releases fluorescent signals with its own sulfurous acid recognition site, detects sulfurous acid based on the Michael addition reaction, and evaluates the pollution degree of sulfur oxides in the water environment through the transformation mode of the sulfur cycle. This probe has high energy transfer efficiency in aqueous solutions. In addition, the fluorescence data obtained by analyzing the water samples were linearly fitted with the gene abundance values of the functional genes of sulfur-producing bacteria, and a significant correlation was obtained. The Kriging interpolation model was used to evaluate the sulfate content distribution at each sampling point to understand the distribution of sulfur oxides in natural water intuitively. The fluorescence signal excited by the probe was also combined with a real-time quantitative polymerase chain reaction (qPCR), and sulfate-reducing and sulfur-oxidizing bacteria were introduced in the sulfur cycle, providing a new method to assess the extent of water pollution effectively.

Sulfur signaling pathway in cardiovascular disease

Hydrogen sulfide (H2S) and sulfur dioxide (SO2), recognized as endogenous sulfur-containing gas signaling molecules, were the third and fourth molecules to be identified subsequent to nitric oxide and carbon monoxide (CO), and exerted diverse biological effects on the cardiovascular system. However, the exact mechanisms underlying the actions of H2S and SO2 have remained elusive until now. Recently, novel post-translational modifications known as S-sulfhydration and S-sulfenylation, induced by H2S and SO2 respectively, have been proposed. These modifications involve the chemical alteration of specific cysteine residues in target proteins through S-sulfhydration and S-sulfenylation, respectively. H2S induced S-sulfhydrylation can have a significant impact on various cellular processes such as cell survival, apoptosis, cell proliferation, metabolism, mitochondrial function, endoplasmic reticulum stress, vasodilation, anti-inflammatory response and oxidative stress in the cardiovascular system. Alternatively, S-sulfenylation caused by SO2 serves primarily to maintain vascular homeostasis. Additional research is warranted to explore the physiological function of proteins with specific cysteine sites, despite the considerable advancements in comprehending the role of H2S-induced S-sulfhydration and SO2-induced S-sulfenylation in the cardiovascular system. The primary objective of this review is to present a comprehensive examination of the function and potential mechanism of S-sulfhydration and S-sulfenylation in the cardiovascular system. Proteins that undergo S-sulfhydration and S-sulfenylation may serve as promising targets for therapeutic intervention and drug development in the cardiovascular system. This could potentially expedite the future development and utilization of drugs related to H2S and SO2.

A unique ratiometric fluorescent probe for detection of SO2 derivatives in living cells and real food samples

Abnormal levels of SO₂ in organisms can cause cardiovascular disease and respiratory allergies. In addition, the amount of SO₂ derivatives used as food preservatives is strictly controlled, and excessive addition can also be harmful to health. Therefore, it is essential to develop a highly sensitive method for the detection of SO₂ and its derivatives in biological systems and real food samples. In this work, a new fluorescent probe (TCMs) with high selectivity and sensitivity for the detection of SO₂ derivatives was reported. The TCMs could quickly identify SO₂ derivatives. It has been successfully used to detect exogenous and endogenous SO₂ derivatives. Furthermore, the TCMs has high sensitivity to SO₂ derivatives in food samples. Moreover, the prepared test strips could be evaluated for the content of SO₂ derivatives in aqueous solutions. This work provides a potential chemical tool to detect SO₂ derivatives in living cells and real food samples.

The Role of Gasotransmitter-Dependent Signaling Mechanisms in Apoptotic Cell Death in Cardiovascular, Rheumatic, Kidney, and Neurodegenerative Diseases and Mental Disorders

Cardiovascular, rheumatic, kidney, and neurodegenerative diseases and mental disorders are a common cause of deterioration in the quality of life up to severe disability and death worldwide. Many pathological conditions, including this group of diseases, are based on increased cell death through apoptosis. It is known that this process is associated with signaling pathways controlled by a group of gaseous signaling molecules called gasotransmitters. They are unique messengers that can control the process of apoptosis at different stages of its implementation. However, their role in the regulation of apoptotic signaling in these pathological conditions is often controversial and not completely clear. This review analyzes the role of nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide (H₂S), and sulfur dioxide (SO₂) in apoptotic cell death in cardiovascular, rheumatic, kidney, and neurodegenerative diseases. The signaling processes involved in apoptosis in schizophrenia, bipolar, depressive, and anxiety disorders are also considered. The role of gasotransmitters in apoptosis in these diseases is largely determined by cell specificity and concentration. NO has the greatest dualism; scales are more prone to apoptosis. At the same time, CO, H₂S, and SO₂ are more involved in cytoprotective processes.

Antidepressant-like effect of endogenous SO2 on depression caused by chronic unpredictable mild stress

Sulfur dioxide (SO₂) is a toxic gas with harmful effects on various organs. However, recent studies have confirmed the protective effect of SO₂ on ischemic heart disease, atherosclerosis, and lung infections. Therefore, the present study was designed to investigate the effect of endogenous SO₂ on depression. The chronic unpredictable mild stress (CUMS) model was performed to cause depression. Depression-like behaviors in animals were determined using an open-field test, forced swimming test, and sucrose consumption. Animal spatial learning and memory were also assessed using the Morris water maze. Besides, the oxidative status of the hippocampus and serum corticosterone level were evaluated. A reduction in the tendency to consume sucrose, mobility, and curiosity, as well as learning and memory disorders were observed in CUMS animals. Depressed animals treated with SO₂ revealed a significant improvement in behavioral and cognitive functions. SO₂ also reduced neuronal damage and lipid peroxidation of the hippocampus and serum corticosterone level in the CUMS group. Various shreds of evidence support a mutual relationship between inflammation and depression; also, growing studies show the role of oxidative stress in the pathogenesis of mood-related disorders such as depression. This study indicated that increased hippocampal malondialdehyde (MDA) and serum corticosterone levels can be due to the existence of oxidative stress and possible activation of inflammatory processes. SO₂ donors diminished MDA and corticosterone levels in depressed animals. According to the study results, SO₂ may be able to reduce tissue damage and eventually behavioral disorders caused by depression by lowering oxidative stress and inflammation.

Gaseous signal molecule SO2 regulates autophagy through PI3K/AKT pathway inhibits cardiomyocyte apoptosis and improves myocardial fibrosis in rats with type II diabetes

Myocardial fibrosis is a key link in the occurrence and development of diabetic cardiomyopathy. Its etiology is complex, and the effect of drugs is not good. Cardiomyocyte apoptosis is an important cause of myocardial fibrosis. The purpose of this study was to investigate the effect of gaseous signal molecule sulfur dioxide (SO₂) on diabetic myocardial fibrosis and its internal regulatory mechanism. Masson and TUNEL staining, Western-blot, transmission electron microscopy, RT-qPCR, immunofluorescence staining, and flow cytometry were used in the study, and the interstitial collagen deposition, autophagy, apoptosis, and changes in phosphatidylinositol 3-kinase (PI3K)/AKT pathways were evaluated from in vivo and in vitro experiments. The results showed that diabetic myocardial fibrosis was accompanied by cardiomyocyte apoptosis and down-regulation of endogenous SO₂-producing enzyme aspartate aminotransferase (AAT)_1/2. However, exogenous SO₂ donors could up-regulate AAT1/2, reduce apoptosis of cardiomyocytes induced by diabetic rats or high glucose, inhibit phosphorylation of PI3K/AKT protein, up-regulate autophagy, and reduce interstitial collagen deposition. In conclusion, the results of this study suggest that the gaseous signal molecule SO₂ can inhibit the PI3K/AKT pathway to promote cytoprotective autophagy and inhibit cardiomyocyte apoptosis to improve myocardial fibrosis in diabetic rats. The results of this study are expected to provide new targets and intervention strategies for the prevention and treatment of diabetic cardiomyopathy.

Natural flavylium-inspired far-red to NIR-II dyes and their applications as fluorescent probes for biomedical sensing

Fluorescent probes that emit in the far-red (600-700 nm), first near-infrared (NIR-I, 700-900 nm), and second NIR (NIR-II, 900-1700 nm) regions possess unique advantages, including low photodamage and deep penetration into biological samples. Notably, NIR-II optical imaging can achieve tissue penetration as deep as 5-20 mm, which is critical for biomedical sensing and clinical applications. Much research has focused on developing far-red to NIR-II dyes to meet the needs of modern biomedicine. Flavylium compounds are natural colorants found in many flowers and fruits. Flavylium-inspired dyes are ideal platforms for constructing fluorescent probes because of their far-red to NIR emissions, high quantum yields, high molar extinction coefficients, and good water solubilities. The synthetic and structural diversities of flavylium dyes also enable NIR-II probe development, which markedly advance the field of NIR-II in vivo imaging. In the last decade, there have been huge developments in flavylium-inspired dyes and their applications as far-red to NIR fluorescent probes for biomedical applications. In this review, we highlight the optical properties of representative flavylium dyes, design strategies, sensing mechanisms, and applications as fluorescent probes for detecting and visualizing important biomedical species and events. This review will prompt further research not only on flavylium dyes, but also into all far-red to NIR fluorophores and fluorescent probes. Moreover, this interest will hopefully spillover into applications related to complex biological systems and clinical treatments, ranging in focus from the sub-organelle to whole-animal levels.

In vivo and in vitro impact of atorvastatin against myocardial ischaemia-reperfusion injury by upregulation of silent information regulator l and attenuation of endoplasmic reticulum stress-induced apoptosis

We aimed to investigate the effects and mechanism of Atorvastatin on Myocardial Ischaemia-Reperfusion Injury in vitro and in vivo. The effects of Atorvastatin on Silent information regulator l (SIRT1) and endoplasmic reticulum (ER) stress were investigated in Myocardial ischaemia-reperfusion (MI/R) injury rat model and hypoxia/reoxygenation (H/R)-treated H9c2 cells. Pathological changes, inflammatory and heart injury markers, cell apoptosis and cell death, SIRT1 and cleaved Caspase-12 expressions, and ER stress relative proteins were measured through HE, enzyme-linked immunosorbent assay, quantitative TUNEL and flow cytometry, immunofluorescence and Western blotting with the assistance of the SIRT1 specific inhibitor EX527 and ER stress pathway blocker treatment. The results of our study demonstrated that atorvastatin treatment attenuated MI/R and H/R mediated inflammatory and heart injury markers, cell apoptosis and cell death, SIRT1 and cleaved Caspase-12 expressions, and ER stress relative protein levels. Finally, we found that atorvastatin reversed SIRT1 expression and blockade the ER stress pathway and increase the cardiomyocytes survival rate in the presence of MI/R and H/R. Our findings provided a new rationale for subsequent academic and clinical research on MI/R injury.

Role of hydrogen sulfide in sulfur dioxide production and vascular regulation

Both hydrogen sulfide (H₂S) and sulfur dioxide (SO₂) are produced endogenously from the mammalian metabolic pathway of sulfur-containing amino acids and play important roles in several vascular diseases. However, their interaction during the control of vascular function has not been fully clear. Here, we investigated the potential role of H₂S in SO₂ production and vascular regulation in vivo and in vitro. Wistar rats were divided into the vehicle, SO₂, DL-propargylglycine (PPG) + SO₂, β-cyano-L-alanine (BCA) + SO₂ and sodium hydrosulfide (NaHS) + SO₂ groups. SO₂ donor was administered with or without pre-administration of PPG, BCA or NaHS for 30 min after blood pressure was stabilized for 1 h, and then, the change in blood pressure was detected by catheterization via the common carotid artery. Rat plasma SO₂ and H₂S concentrations were measured by high performance liquid chromatography and sensitive sulfur electrode, respectively. The isolated aortic rings were prepared for the measurement of changes in vasorelaxation stimulated by SO₂ after PPG, BCA or NaHS pre-incubation. Results showed that the intravenous injection of SO₂ donors caused transient hypotension in rats compared with vehicle group. After PPG or BCA pretreatment, the plasma H₂S content decreased but the SO₂ content increased markedly, and the hypotensive effect of SO₂ was significantly enhanced. Conversely, NaHS pretreatment upregulated the plasma H₂S content but reduced SO₂ content, and attenuated the hypotensive effect of SO₂. After PPG or BCA pre-incubation, the vasorelaxation response to SO₂ was enhanced significantly. While NaHS pre-administration weakened the SO₂-induced relaxation in aortic rings. In conclusion, our in vivo and in vitro data indicate that H₂S negatively controls the plasma content of SO₂ and the vasorelaxant effect under physiological conditions.

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.

Near-infrared light-triggered nano-prodrug for cancer gas therapy

Gas therapy (GT) has attracted increasing attention in recent years as a new cancer treatment method with favorable therapeutic efficacy and reduced side effects. Several gas molecules, such as nitric oxide (NO), carbon monoxide (CO), hydrogen (H2), hydrogen sulfide (H2S) and sulfur dioxide (SO2), have been employed to treat cancers by directly killing tumor cells, enhancing drug accumulation in tumors or sensitizing tumor cells to chemotherapy, photodynamic therapy or radiotherapy. Despite the great progress of gas therapy, most gas molecules are prone to nonspecific distribution when administered systemically, resulting in strong toxicity to normal tissues. Therefore, how to deliver and release gas molecules to targeted tissues on demand is the main issue to be considered before clinical applications of gas therapy. As a specific and noninvasive stimulus with deep penetration, near-infrared (NIR) light has been widely used to trigger the cleavage and release of gas from nano-prodrugs via photothermal or photodynamic effects, achieving the on-demand release of gas molecules with high controllability. In this review, we will summarize the recent progress in cancer gas therapy triggered by NIR light. Furthermore, the prospects and challenges in this field are presented, with the hope for ongoing development.

Cellular Response to Unfolded Proteins in Depression

Despite many scientific studies on depression, there is no clear conception explaining the causes and mechanisms of depression development. Research conducted in recent years has shown that there is a strong relationship between depression and the endoplasmic reticulum (ER) stress. In order to restore ER homeostasis, the adaptive unfolded protein response (UPR) mechanism is activated. Research suggests that ER stress response pathways are continuously activated in patients with major depressive disorders (MDD). Therefore, it seems that the recommended drugs should reduce ER stress. A search is currently underway for drugs that will be both effective in reducing ER stress and relieving symptoms of depression.

Diketopyrrolopyrrole-based fluorescent probe for endogenous bisulfite detection and bisulfite triggered phototoxicity specific in liver cancer cells

As the main existing form of SO₂ derivatives, bisulfite showed closely relationship to many diseases. In this work, a new fluorescent probe (SDPP-DM) based on thienyl-substituted diketopyrrolopyrrole (SDPP) was designed and synthesized for the detection of endogenous bisulfite. The probe displayed obvious color changes from green to pink towards bisulfite due to the reduced conjugated length caused by the addition to the α,β-unsaturated double bond of its structure, and the change of the fluorescence intensity of SDPP-DM (I/I₀) was about 16 folds. In addition, SDPP-DM was prepared a test strip for bisulfite identified by naked eye through color and fluorescence changes. Besides, SDPP-DM was successfully applied to imaging and discriminating different endogenous bisulfite levels in normal and cancer cells of liver. More importantly, the ROS generation and cell viability tests showed the phototoxicity of SDPP-DM triggered by bisulfite, indicating the specific phototoxicity of SDPP-DM towards liver cancer cells than normal liver cells.

Compensatory role of endogenous sulfur dioxide in nitric oxide deficiency-induced hypertension

OBJECTIVE

This study aimed to determine the communicational pattern of gaseous signaling molecules sulfur dioxide (SO2) and nitric oxide (NO) between vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs), and elucidate the compensatory role and significance of endogenous SO2 in the development of hypertension due to NO deficiency.

APPROACH AND RESULTS

Blood pressure was monitored by the tail-cuff and implantable physiological signal telemetry in L-nitro-arginine methyl ester (l-NAME)-induced hypertensive mice, and structural alterations of mouse aortic vessels were detected by the elastic fiber staining method. l-NAME-treated mice showed decreased plasma NO levels, increased SO2 levels, vascular remodeling, and increased blood pressure, and application of l-aspartate-β-hydroxamate, which inhibits SO2 production, further aggravated vascular structural remodeling and increased blood pressure. Moreover, in a co-culture system of HAECs and HASMCs, NO from HAECs did not influence aspartate aminotransferase (AAT)1 protein expression but decreased AAT1 activity in HASMCs, thereby resulting in the inhibition of endogenous SO2 production. Furthermore, NO promoted S-nitrosylation of AAT1 protein in HASMCs and purified AAT1 protein. Liquid chromatography with tandem mass spectrometry showed that the Cys192 site of AAT1 purified protein was modified by S-nitrosylation. In contrast, dithiothreitol or C192S mutations in HASMCs blocked NO-induced AAT1 S-nitrosylation and restored AAT1 enzyme activity.

CONCLUSION

Endothelium-derived NO inhibits AAT activity by nitrosylating AAT1 at the Cys192 site and reduces SO2 production in HASMCs. Our findings suggest that SO2 acts as a compensatory defense system to antagonize vascular structural remodeling and hypertension when the endogenous NO pathway is disturbed.

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.

H2S donor molecules against cold ischemia-reperfusion injury in preclinical models of solid organ transplantation

Cold ischemia-reperfusion injury (IRI) is an inevitable and unresolved problem that poses a great challenge in solid organ transplantation (SOT). It represents a major factor that increases acute tubular necrosis, decreases graft survival, and delays graft function. This complicates graft quality, post-transplant patient care and organ transplantation outcomes, and therefore undermines the success of SOT. Herein, we review recent advances in research regarding novel pharmacological strategies involving the use of different donor molecules of hydrogen sulfide (H₂S), the third established member of the gasotransmitter family, against cold IRI in different experimental models of SOT (kidney, heart, lung, liver, pancreas and intestine). Additionally, we discuss the molecular mechanisms underlying the effects of these H₂S donor molecules in SOT, and suggestions for clinical translation. Our reviewed findings showed that storage of donor organs in H₂S-supplemented preservation solution or administration of H₂S to organ donor prior to organ procurement and to recipient at the start and during reperfusion is a novel, simple and cost-effective pharmacological approach to minimize cold IRI, limit post-transplant complications and improve transplantation outcomes. In conclusion, experimental evidence demonstrate that H₂S donors can significantly mitigate cold IRI during SOT through inhibition of a complex cascade of interconnected cellular and molecular events involving microcirculatory disturbance and microvascular dysfunction, mitochondrial injury, inflammatory responses, cell damage and cell death, and other damaging molecular pathways while promoting protective pathways. Translating these promising findings from bench to bedside will lay the foundation for the use of H₂S donor molecules in clinical SOT in the future.

Self-Propelled Asymmetrical Nanomotor for Self-Reported Gas Therapy

Gas therapy has emerged as a new therapeutic strategy in combating cancer owing to its high therapeutic efficacy and biosafety. However, the clinical translation of gas therapy remains challenging due to the rapid diffusion and limited tissue penetration of therapeutic gases. Herein, a self-propelled, asymmetrical Au@MnO₂ nanomotor for efficient delivery of therapeutic gas to deep-seated cancer tissue for enhanced efficacy of gas therapy, is reported. The Au@MnO₂ nanoparticles (NPs) catalyze endogenous H₂ O₂ into O₂ that propels NPs into deep solid tumors, where SO₂ prodrug is released from the hollow NPs owing to the degradation of MnO₂ shells. Fluorescein isothiocyanate (FITC) is conjugated onto the surface of Au via caspase-3 responsive peptide (DEVD) and the therapeutic process of gas therapy can be optically self-reported by the fluorescence of FITC that is turned on in the presence of overexpressed caspase-3 as an apoptosis indicator. Au@MnO₂ nanomotors show self-reported therapeutic efficacy and high biocompatibility both in vitro and in vivo, offering important new insights to the design and development of novel nanomotors for efficient payload delivery into deep tumor tissue and in situ monitoring of the therapeutic process.

Sulfur Dioxide: An Endogenous Protector Against Myocardial Injury

Sulfur dioxide (SO2) was previously known as a harmful gas in air pollution. Recently, it was reported that SO2 can be endogenously generated in cardiovascular tissues. Many studies have revealed that endogenous SO2 has important physiological and pathophysiological significance and pharmacological potential. As a novel gasotransmitter, SO2 has important regulatory effects on the heart. It has a dose-dependent negative inotropic effect on cardiac function, in which L-type calcium channels are involved. SO2 can also attenuate myocardial injury caused by various harmful stimuli and play an important role in myocardial ischemia-reperfusion injury and myocardial hypertrophy. These effects are thought to be linked to its ability to reduce inflammation and as an antioxidant. In addition, SO2 regulates cardiomyocyte apoptosis and autophagy. Therefore, endogenous SO2 plays an important role in maintaining cardiovascular system homeostasis. In the present review, the literature concerning the metabolism of endogenous SO2, its cardiac toxicological effects and physiological regulatory effects, mechanisms for SO2-mediated myocardial protection and its pharmacological applications are summarized and discussed.

Electroacupuncture Pretreatment Mitigates Myocardial Ischemia/Reperfusion Injury via XBP1/GRP78/Akt Pathway

Myocardial ischemia/reperfusion injury is a common clinical problem and can result in severe cardiac dysfunction. Previous studies have demonstrated the protection of electroacupuncture against myocardial ischemia/reperfusion injury. However, the role of X-box binding protein I (XBP1) signaling pathway in the protection of electroacupuncture was still elusive. Thus, we designed this study and demonstrated that electroacupuncture significantly improved cardiac function during myocardial ischemia/reperfusion injury and reduced cardiac infarct size. Electroacupuncture treatment further inhibited cardiac injury manifested by the decrease of the activities of serum lactate dehydrogenase and creatine kinase-MB. The results also revealed that electroacupuncture elevated the expressions of XBP1, glucose-regulated protein 78 (GRP78), Akt, and Bcl-2 and decreased the Bax and cleaved Caspase 3 expressions. By using the inhibitor of XBP1 in vitro, the results revealed that suppression of XBP1 expression could markedly increase the activities of lactate dehydrogenase and creatine kinase-MB and cell apoptosis, thus exacerbating stimulated ischemia/reperfusion-induced H9c2 cell injury. Compared with stimulated ischemia/reperfusion group, inhibition of XBP1 inhibited the downstream GRP78 and Akt expressions during stimulated ischemia/reperfusion injury. Collectively, our data demonstrated that electroacupuncture treatment activated XBP1/GRP78/Akt signaling to protect hearts from myocardial ischemia/reperfusion injury. These findings revealed the underlying mechanisms of electroacupuncture protection against myocardial ischemia/reperfusion injury and may provide novel therapeutic targets for the clinical treatment of myocardial ischemia/reperfusion injury.

A single small molecule fluorescent probe for imaging RNA distribution and detecting endogenous SO2 through distinct fluorescence channels

Herein, we developed a novel small molecule fluorescent probe for imaging the distribution of RNA and detecting endogenous SO2 through distinct fluorescence channels in cells.

Effect of sulfur dioxide on vascular biology

Gasotransmitters, such as nitric oxide, carbon monoxide and hydrogen sulfide, can be generated endogenously. These gasotransmitters play important roles in vascular biology, including vasorelaxation and inhibition of vascular smooth muscle cell (VSMC) proliferation. In recent years, sulfur dioxide (SO₂) has been considered as a fourth gasotransmitter. SO₂ is present in air pollution. Moreover, SO₂ toxicity, including oxidative stress and DNA damage, has been extensively reported in previous studies. Recent studies have shown that SO₂ can be endogenously generated in various organs and vascular tissues, where it regulates vascular tone, vascular smooth cell proliferation and collagen synthesis. SO₂ can decrease blood pressure in rats, inhibit smooth muscle cell proliferation and collagen accumulation and promote collagen degradation, and improve vascular remodelling. SO₂ can decrease cardiovascular atherosclerotic plaques by enhancing the antioxidant effect and upregulating nitric oxide/nitric oxide synthase and hydrogen sulfide/cystathionine-γ-lyase pathways. SO₂ can also ameliorate vascular calcification via the transforming growth factor - β1/Smad pathway. The effect of SO₂ on vascular regulation has attracted great interest. SO₂ may be a novel mediator in vascular biology.

Prodrugs of Persulfides, Sulfur Dioxide, and Carbon Disulfide: Important Tools for Studying Sulfur Signaling at Various Oxidation States

Significance: Bioactive sulfur species such as hydrogen sulfide (H₂S), persulfide species (R-S_nSH, n ≥ 1), hydrogen polysulfide (H₂S_n, n ≥ 2), sulfur dioxide (SO₂), and carbon disulfide (CS₂) participate in various physiological and/or pathological pathways such as vasodilation, apoptosis, inflammation, and energy metabolism regulation. The oxidation state of the individual sulfur species endows them unique biological activities. Recent Advances: There have been great strides made in achieving molecular understanding of the sulfur-signaling processes. Critical Issues: The development of various chemical tools that deliver reactive sulfur species in a controllable manner has played an important role in understanding the different roles of various sulfur species. In this review, we focus on three types of sulfur species, including persulfide, SO₂, and CS₂. Starting with a brief introduction of their physiological functions, we will then assess the various drug delivery strategies to generate persulfide species, SO₂, and CS₂ as research tools and potentially as therapeutic agents. Future Directions: Development of donors of various sulfur species that respond to distinct stimulus is critical for this field. Another key to the long-term success of this field is the identification of an area of unmet medical need that can be addressed with these sulfur species.

Diazoxide Protects against Myocardial Ischemia/Reperfusion Injury by Moderating ERS via Regulation of the miR-10a/IRE1 Pathway

Nowadays, reperfusion is still the most effective treatment for ischemic heart disease. However, cardiac reperfusion therapy would lead to reperfusion injury, which may have resulted from endoplasmic reticulum stress (ERS) during reperfusion. Diazoxide (DZ) is a highly selective mitochondrial adenosine triphosphate-sensitive potassium channel opener. Its protective effect on I/R injury has been confirmed in many organs such as the heart and brain. However, the mechanism of its protective effect has not been fully elucidated. MicroRNAs (miRNAs) are widely involved in pathologies of heart disease. In this study, we found that miR-10a expression was highly upregulated in the myocardial I/R groups, and DZ treatment significantly reduced the expression of miR-10a. More importantly, we found that DZ treatment can moderate ERS via regulation of the miR-10a/IRE1 pathway in the I/R and H/R models, thereby protecting myocardial H/R injury.

Role of endoplasmic reticulum oxidase 1α in H9C2 cardiomyocytes following hypoxia/reoxygenation injury

Endoplasmic reticulum (ER) oxidase 1α (ERO1α) is a glycosylated flavoenzyme that is located on the luminal side of the ER membrane, which serves an important role in catalyzing the formation of protein disulfide bonds and ER redox homeostasis. However, the role of ERO1α in myocardial hypoxia/reoxygenation (H/R) injury remains largely unknown. In the present study, ERO1α expression levels in H9C2 cardiomyocytes increased following H/R, reaching their highest levels following 3 h of hypoxia and 6 h of reoxygenation. In addition, H/R induced apoptosis, and significantly increased expression levels of ER stress (ERS) markers 78 kDa glucose-regulated protein and C/EBP homologous protein. Moreover, the genetic knockdown of ERO1α using short hairpin RNA suppressed cell apoptosis, caspase-3 activity, expression levels of cleaved caspase-12 and cytochrome c in the cytoplasm. Overall, this suggested that ERO1α knockdown may protect against H/R injury. The ERS activator tunicamycin (TM) was used to counteract the ERO1α-induced reduction in ERS; however, the percentage of apoptotic cells and the level of mitochondrial damage did not change. In conclusion, the results from the present study suggested that ERO1α knockdown may protect H9C2 cardiomyocytes from H/R injury through inhibiting intracellular ROS production and increasing intracellular levels of Ca²⁺, suggesting that ERO1α may serve an important role in H/R.

Negative auto-regulation of sulfur dioxide generation in vascular endothelial cells: AAT1 S-sulfenylation

Recently, endogenous sulfur dioxide (SO2) has been found to exert an important function in the cardiovascular system. However, the regulatory mechanism for SO2 generation has not been entirely clarified. Hence, we aimed to explore the possible auto-regulation of endogenous SO2 generation and its mechanisms in vascular endothelial cells. We showed that SO2 did not affect the protein expression of aspartate aminotransferase 1 (AAT1), a major SO2 synthesis enzyme, but significantly inhibited AAT activity in primary human umbilical vein endothelial cells (HUVECs) and porcine purified AAT1 protein. An AAT1 enzymatic kinetic study showed that SO2 reduced the Vmax (1.89 ± 0.10 vs 2.55 ± 0.12, μmol/mg/min, P < 0.05) and increased the Km (35.97 ± 9.54 vs 19.33 ± 1.76 μmol/L, P < 0.05) values. Furthermore, SO2 induced S-sulfenylation of AAT1 in primary HUVECs and purified AAT1 protein. LC-MS/MS analysis indicated that SO2 sulfenylated AAT1 at Cys192. Mechanistically, thiol reductant DTT treatment or C192S mutation prevented SO2-induced AAT1 sulfenylation and the subsequent inhibition of AAT activity in purified AAT1 protein and primary HUVECs. Our findings reveal, for the first time, a mechanism of auto-regulation of SO2 generation through sulfenylation of AAT1 at Cys192 to suppress AAT activity in vascular endothelial cells. These findings will greatly deepen the understanding of regulatory mechanisms in the cardiovascular homeostasis.

Hydrogen Sulfide Plays an Important Protective Role through Influencing Endoplasmic Reticulum Stress in Diseases

The endoplasmic reticulum is an important organelle responsible for protein synthesis, modification, folding, assembly and transport of new peptide chains. When the endoplasmic reticulum protein folding ability is impaired, the unfolded or misfolded proteins accumulate to lead to endoplasmic reticulum stress. Hydrogen sulfide is an important signaling molecule that regulates many physiological and pathological processes. Recent studies indicate that H₂S plays an important protective role in many diseases through influencing endoplasmic reticulum stress, but its mechanism is not fully understood. This article reviewed the progress about the effect of H₂S on endoplasmic reticulum stress and its mechanisms involved in diseases in recent years to provide theoretical basis for in-depth study.

A near-infrared fluorescent probe for ratiometric sensing of SO2 in cells and zebrafish

SO₂ sensing and imaging: the first near-infrared fluorescent probe Mito-HN with AIEE characteristics for ratiometric sensing of SO₂ derivatives in vitro, in cells, and in zebrafish was rationally designed and synthesized.

Amino Acids in Circulatory Function and Health

Cardiovascular disease is the major cause of global mortality and disability. Abundant evidence indicates that amino acids play a fundamental role in cardiovascular physiology and pathology. Decades of research established the importance of L-arginine in promoting vascular health through the generation of the gas nitric oxide. More recently, L-glutamine, L-tryptophan, and L-cysteine have also been shown to modulate vascular function via the formation of a myriad of metabolites, including a number of gases (ammonia, carbon monoxide, hydrogen sulfide, and sulfur dioxide). These amino acids and their metabolites preserve vascular homeostasis by regulating critical cellular processes including proliferation, migration, differentiation, apoptosis, contractility, and senescence. Furthermore, they exert potent anti-inflammatory and antioxidant effects in the circulation, and block the accumulation of lipids within the arterial wall. They also mitigate known risk factors for cardiovascular disease, including hypertension, hyperlipidemia, obesity, and diabetes. However, in some instances, the metabolism of these amino acids through discrete pathways yields compounds that fosters vascular disease. While supplementation with amino acid monotherapy targeting the deficiency has ameliorated arterial disease in many animal models, this approach has been less successful in the clinic. A more robust approach combining amino acid supplementation with antioxidants, anti-inflammatory agents, and/or specific amino acid enzymatic pathway inhibitors may prove more successful. Alternatively, supplementation with amino acid-derived metabolites rather than the parent molecule may elicit beneficial effects while bypassing potentially harmful pathways of metabolism. Finally, there is an emerging recognition that circulating levels of multiple amino acids are perturbed in vascular disease and that a more holistic approach that targets all these amino acid derangements is required to restore circulatory function in diseased blood vessels.

Nobiletin ameliorates myocardial ischemia and reperfusion injury by attenuating endoplasmic reticulum stress-associated apoptosis through regulation of the PI3K/AKT signal pathway

BACKGROUND

Nobiletin is a natural polymethoxylated flavone that confers antioxidative, anti-inflammatory and anti-apoptotic efficacies. However, the potential benefits of nobiletin preconditioning on myocardial ischemia and reperfusion injury (MIRI) remains largely unknown.

METHODS

MIRI was induced by ligation of the left anterior descending coronary artery and reperfusion. Pre-treatment with nobiletin, with or without PI3K/AKT inhibitor LY294002, was performed at the onset of reperfusion. Histological analyses, apoptotic evaluation, plasma biomarkers of myocardial injury, echocardiographic evaluation of cardiac function and myocardial levels of endoplasmic reticulum stress (ERS)-related molecules were observed.

RESULTS

Nobiletin pre-treatment significantly deceased the infract size and number of apoptotic cells in the myocardium of MIRI rats, as determined by Terminal deoxynucleotidyl transferase dUTP nick end labeling staining. Moreover, the plasma levels of lactate dehydrogenase (LDH) and creatine kinase-MB (CK-MB) also markedly decreased. In addition, pre-treatment with nobiletin restored the impaired cardiac systolic function, as evidenced by echocardiographic evaluation results. Importantly, pre-treatment with nobiletin significantly downregulated the myocardial mRNA and protein levels of ERS-related signal molecules, including GRP78, CHOP and caspase-12, but upregulated the levels of p-PI3K and p-AKT. Interestingly, co-treatment with LY294002 significantly abolished the benefits of nobiletin pre-treatment on cardiac function, myocardial apoptosis, cardiomyocyte injuries, and changes in myocardial levels of ERS-related signaling molecules.

CONCLUSION

Nobiletin pre-treatment may alleviate MIRI probably via the attenuation of PI3K/AKT-mediated ERS-related myocardial apoptosis.

Inhibitory Effects of Sulfur Dioxide on Rat Myocardial Fibroblast Proliferation and Migration

Background:

Myocardial fibrosis is an important pathological change in many heart diseases, but its pathogenesis is very complex and has not yet been fully elucidated. The study was designed to examine whether endogenous sulfur dioxide (SO₂) is a novel myocardial fibroblast proliferation and migration inhibitor.

Methods:

Primary rat myocardial fibroblasts were isolated and transfected with aspartate aminotransferase (AAT1 and AAT2) knockdown lentivirus or empty lentivirus. SO₂ content in the supernatant was determined with high-performance liquid chromatography, and the expressions of AAT1, AAT2, proliferating cell nuclear antigen (PCNA), phosphorylated extracellular signal-regulated protein kinase (p-ERK), and total ERK (T-ERK) in the cells were detected. Cell migration was detected by wound healing test. Independent sample t-test (for two groups) and one-way analysis of variance (three or more groups) were used to analyze the results.

Results:

Both AAT1 and AAT2 knockdown significantly reduced SO₂ levels (F = 31.46, P < 0.01) and AAT1/2 protein expression (AAT1, t = 12.67, P < 0.01; AAT2, t = 9.61, P < 0.01), but increased PCNA expression and Cell Counting Kit-8 (CCK-8) activity as well as the migration in rat primary myocardial fibroblasts (P < 0.01). Supplementation of SO₂ rather than pyruvate significantly inhibited the increase in proliferation and migration caused by AAT knockdown (P < 0.01). Mechanistically, the ratio of p-ERK to T-ERK was significantly increased in the AAT1/2 knockdown groups compared with that in the empty lentivirus group (AAT1, t = −7.36, P < 0.01; AAT2, t = −10.97, P < 0.01). Whereas PD98059, an inhibitor of ERK activation, successfully blocked AAT knockdown-induced PCNA upregulation (F = 74.01, P > 0.05), CCK-8 activation (F = 50.14, P > 0.05), and migration augmentation in myocardial fibroblasts (24 h, F = 37.08, P > 0.05; 48 h, F = 58.60, P > 0.05).

Conclusion:

Endogenous SO₂ might be a novel myocardial fibroblast proliferation and migration inhibitor via inhibiting the ERK signaling pathway.

SO2 Donors and Prodrugs, and Their Possible Applications: A Review

SO2 is widely recognized as an air pollutant and is a known cause of acid rain. At a sufficiently high level, it also causes respiratory diseases. A much lesser known side of SO2 is its endogenous nature and possible physiological roles. There is mounting evidence that SO2 is produced during normal cellular metabolism and may possibly function as a signaling molecule in normal physiology. The latter aspect is still at the stage of being carefully examined as to the validity of classifying SO2 as a gasotransmitter with endogenous signaling roles. One difficulty in studying the biological and pharmacological roles of SO2 is the lack of adequate tools for its controllable and precise delivery. Traditional methods of using SO2 gas or mixed sulfite salts do not meet research need for several reasons. Therefore, there has been increasing attention on the need of developing SO2 donors or prodrugs that can be used as tools for the elucidation of SO2's physiological roles, pharmacological effects, and possible mechanism(s) of action. In this review, we aim to review basic sulfur chemistry in the context of sulfur signaling and various chemical strategies used for designing SO2 donors. We will also discuss potential pharmacological applications of SO2 donors, lay out desirable features for such donors and possibly prodrugs, analyze existing problems, and give our thoughts on research needs.

Sulfur dioxide attenuates sepsis-induced cardiac dysfunction via inhibition of NLRP3 inflammasome activation in rats

OBJECTIVE

Sulfur dioxide (SO₂) plays an important role in maintaining homeostasis of cardiovascular system. This study was aimed to investigate cardioprotective effects of SO₂ on in the rat and the underlying mechanism.

METHODS AND RESULTS

Sepsis model induced by cecal ligation and puncture (CLP) in rats were used. SO₂ donor (NaHSO₃/Na₂SO₃, 1:3 M/M) was administered intraperitoneally at a dose of 85 mg/kg. Primary neonatal rat cardiac ventricular myocytes (NRCMs) were stimulated with LPS (1 mg/mL) in presence or absence of different concentrations of SO₂ (10, 50 and 100 μmol/L). SO₂ donor could restore the decreased levels of SO₂ in plasma and heart of septic rats. SO₂ exhibited dramatic improvement in cardiac functions. At 24 h after CLP, SO₂ treatments decreased the number of TUNEL-positive cells, Bax/Bcl-2 ratio and activity of caspase-3. Moreover CLP-induced inflammatory response was also relieved by SO₂. In NRCMs, SO₂ could suppress the LPS-induced myocardial injury, leading to an increase in cell viability, a decrease in LDH and apoptotic rate. Western blot showed that the expression of TLR4, NLRP3, and Caspase-1 were obviously increased in myocardial tissue of CLP group or in NRCMs of LPS group, while SO₂ significantly inhibited the CLP-induced or LPS-induced TLR4, NLRP3, and Caspase-1 expression.

CONCLUSION

SO₂ attenuated sepsis-induced cardiac dysfunction likely in association with the inhibiting inflammation via TLR4/NLRP3 signaling pathway.

The cardioprotective effect of dexmedetomidine on regional ischemia/reperfusion injury in type 2 diabetic rat hearts

BACKGROUND

Dexmedetomidine (DEX) is an α₂-adrenergic receptor agonist commonly used during perioperative periods due to its sedation and analgesia effect. It is confirmed that DEX has cardioprotective effects against ischemia/reperfusion (I/R) injury. We investigated whether DEX administration is beneficial to type 2 diabetic rats subjected to I/R injury.

METHODS

The diabetes model was established by providing a high-fat diet for 2 weeks followed by injecting 35 mg/kg streptozotocin (STZ). The myocardial I/R model consisted of left anterior descending coronary artery occlusion for 30 min followed by reperfusion for two-hours. DEX was administered before ischemia; alternatively, yohimbine was administered with or without DEX before ischemia. At the end of reperfusion, the rats were sacrificed, and hearts were isolated for histology. The levels of glycogen synthase kinase-3β (GSK-3β) and phosphorylated GSK-3β (p-GSK-3β) were quantitatively analyzed. The infarct size was measured via Evans Blue and 2,3,5‑triphenyltetrazolium chloride (TTC) staining. Plasma samples were collected to measure the levels of cardiac Troponin T (cTnT). Arrhythmia scores were recorded during the first few minutes of reperfusion.

RESULTS

DEX preconditioning significantly reduced myocardial infarct size, arrhythmia scores and the plasma cTnT levels, and increased the p-GSK-3β levels. All of these protective effects of DEX were reversed by co-administration of yohimbine.

CONCLUSIONS

These results suggested that DEX preconditioning exerted a cardioprotective effect against regional I/R injury in diabetic rats.

Short-term effects of ambient air pollutants and myocardial infarction in Changzhou, China

Ambient air pollution had been shown strongly associated with cardiovascular diseases. However, the association between air pollution and myocardial infarction (MI) is inconsistent. In the present study, we conducted a time-series study to investigate the association between air pollution and MI. Daily air pollutants, weather data, and MI data were collected from January 2015 to December 2016 in Changzhou, China. Generalized linear model (GLM) was used to assess the immediate effects of air pollutants (PM_2.5, PM₁₀, NO₂, SO₂, and O₃) on MI. We identified a total of 5545 cases for MI, and a 10-μg/m³ increment in concentrations of PM_2.5 and PM₁₀ was associated with respective increases of 1.636% (95% confidence interval [CI] 0.537-2.740%) and 0.805% (95% CI 0.037-1.574%) for daily MI with 2-day cumulative effects. The associations were more robust among males and in the warm season versus the cold one. No significant effect was found in SO₂, NO₂, or O₃. This study suggested that short-term exposure to PM_2.5 and PM₁₀ was associated with the increased MI risks. Our results might be useful for the primary prevention of MI exacerbated by air pollutants.

The Increased Endogenous Sulfur Dioxide Acts as a Compensatory Mechanism for the Downregulated Endogenous Hydrogen Sulfide Pathway in the Endothelial Cell Inflammation

Endogenous hydrogen sulfide (H₂S) and sulfur dioxide (SO₂) are regarded as important regulators to control endothelial cell function and protect endothelial cell against various injuries. In our present study, we aimed to investigate the effect of endogenous H₂S on the SO₂ generation in the endothelial cells and explore its significance in the endothelial inflammation in vitro and in vivo. The human umbilical vein endothelial cell (HUVEC) line (EA.hy926), primary HUVECs, primary rat pulmonary artery endothelial cells (RPAECs), and purified aspartate aminotransferase (AAT) protein from pig heart were used for in vitro experiments. A rat model of monocrotaline (MCT)-induced pulmonary vascular inflammation was used for in vivo experiments. We found that endogenous H₂S deficiency caused by cystathionine-γ-lyase (CSE) knockdown increased endogenous SO₂ level in endothelial cells and enhanced the enzymatic activity of AAT, a major SO₂ synthesis enzyme, without affecting the expressions of AAT1 and AAT2. While H₂S donor could reverse the CSE knockdown-induced increase in the endogenous SO₂ level and AAT activity. Moreover, H₂S donor directly inhibited the activity of purified AAT protein, which was reversed by a thiol reductant DTT. Mechanistically, H₂S donor sulfhydrated the purified AAT1/2 protein and rescued the decrease in the sulfhydration of AAT1/2 protein in the CSE knockdown endothelial cells. Furthermore, an AAT inhibitor l-aspartate-β-hydroxamate (HDX), which blocked the upregulation of endogenous SO₂/AAT generation induced by CSE knockdown, aggravated CSE knockdown-activated nuclear factor-κB pathway in the endothelial cells and its downstream inflammatory factors including ICAM-1, TNF-α, and IL-6. In in vivo experiment, H₂S donor restored the deficiency of endogenous H₂S production induced by MCT, and reversed the upregulation of endogenous SO₂/AAT pathway via sulfhydrating AAT1 and AAT2. In accordance with the results of the in vitro experiment, HDX exacerbated the pulmonary vascular inflammation induced by the broken endogenous H₂S production in MCT-treated rat. In conclusion, for the first time, the present study showed that H₂S inhibited endogenous SO₂ generation by inactivating AAT via the sulfhydration of AAT1/2; and the increased endogenous SO₂ generation might play a compensatory role when H₂S/CSE pathway was downregulated, thereby exerting protective effects in endothelial inflammatory responses in vitro and in vivo.

A single fluorescent probe for imaging ribonucleic acid and sulfur dioxide in living systems and its unique application in tumor and normal cells

Herein, the development of EPI-RS is described as the first paradigm of a probe that could image RNA and SO₂ with distinct fluorescence signals in living systems.

A ratiometric fluorescence probe for rapid detection of mitochondrial SO2 derivatives

In this study, we report a fluorescent probe (CBT) for detecting SO₂ derivatives in ratiometric fluorescence manner.

Sulphur dioxide suppresses inflammatory response by sulphenylating NF-κB p65 at Cys38 in a rat model of acute lung injury

The present study was designed to investigate whether endogenous sulphur dioxide (SO2) controlled pulmonary inflammation in a rat model of oleic acid (OA)-induced acute lung injury (ALI). In this model, adenovirus expressing aspartate aminotransferase (AAT) 1 was delivered to the lungs, and the levels of SO2 and proinflammatory cytokines in rat lung tissues were measured. In the human alveolar epithelial cell line A549, the nuclear translocation and DNA binding activities of wild-type (wt) and C38S (cysteine-to-serine mutation at p65 Cys38) NF-κB p65 were detected. GFP-tagged C38S p65 was purified from HEK 293 cells and the sulphenylation of NF-κB p65 was studied. OA caused a reduction in SO2/AAT pathway activity but increased pulmonary inflammation and ALI. However, either the presence of SO2 donor, a combination of Na2SO3 and NaHSO3, or AAT1 overexpression in vivo successfully blocked OA-induced pulmonary NF-κB p65 phosphorylation and consequent inflammation and ALI. Either treatment with an SO2 donor or overexpression of AAT1 down-regulated OA-induced p65 activity, but AAT1 knockdown in alveolar epithelial cells mimicked OA-induced p65 phosphorylation and inflammation in vitro. Mechanistically, OA promoted NF-κB nuclear translocation, DNA binding activity, recruitment to the intercellular cell adhesion molecule (ICAM)-1 promoter, and consequent inflammation in epithelial cells; these activities were reduced in the presence of an SO2 donor. Furthermore, SO2 induced sulphenylation of p65, which was blocked by the C38S mutation on p65 in epithelial cells. Hence, down-regulation of SO2/AAT is involved in pulmonary inflammation during ALI. Furthermore, SO2 suppressed inflammation by sulphenylating NF-κB p65 at Cys38.

Bisoprolol protects myocardium cells against ischemia/reperfusion injury by attenuating unfolded protein response in rats

Bisoprolol (B) exerts potential cardioprotective effects against myocardial ischemia/reperfusion (I/R) injury. Unfolded protein response (UPR) attenuates I/R injury induced apoptosis by reducing oxidative damage and inflammation response. The current study investigated whether the protective effects of bisoprolol resulted from modulating UPR and anti-inflammatory during myocardial I/R condition and elucidated its potential mechanisms. Sprague-Dawley rats were treated with B in the absence or presence of the injected UPR activator dithiothreitol (DTT) and then subjected to myocardial I/R surgery. In vitro, cultured H9C2 cells were pretreated with B or DTT and then subjected to simulate ischemia reperfusion (SIR) operation. Bisoprolol conferred cardioprotective effects by improving postischemic cardiac function, decreasing infarct size, reducing apoptotic index, diminishing serum creatine kinase and lactate dehydrogenase levels, suppressing TNF-α and IL-6 secretion, inhibiting UPR signal pathways and downregulating caspase-12 and caspase-3 expressions. Consistently, B conferred similar antioxidative and anti-inflammatory effects against SIR injury in cultured H9C2 cardiomyocytes. Pretreatment with DTT or C/EBP homologous protein (CHOP) overexpression mediated by lentivirus administration both abolished these effects. In summary, our results demonstrate that Bisoprolol protects myocardium cells against ischemia/reperfusion injury partly by attenuating unfolded protein response.

Sulfur Dioxide Inhibits Extracellular Signal-regulated Kinase Signaling to Attenuate Vascular Smooth Muscle Cell Proliferation in Angiotensin II-induced Hypertensive Mice

Background:

Clarifying the mechanisms underlying vascular smooth muscle cell (VSMC) proliferation is important for the prevention and treatment of vascular remodeling and the reverse of hyperplastic lesions. Previous research has shown that the gaseous signaling molecule sulfur dioxide (SO₂) inhibits VSMC proliferation, but the mechanism for the inhibition of the angiotensin II (AngII)-induced VSMC proliferation by SO₂ has not been fully elucidated. This study was designed to investigate if SO₂ inhibited VSMC proliferation in mice with hypertension induced by AngII.

Methods:

Thirty-six male C57 mice were randomly divided into control, AngII, and AngII + SO₂ groups. Mice in AngII group and AngII + SO₂ group received a capsule-type AngII pump implanted under the skin of the back at a slow-release dose of 1000 ng·kg⁻¹·min⁻¹. In addition, mice in AngII + SO₂ received intraperitoneal injections of SO₂ donor. Arterial blood pressure of tail artery was determined. The thickness of the aorta was measured by elastic fiber staining, and proliferating cell nuclear antigen (PCNA) and phosphorylated-extracellular signal-regulated kinase (P-ERK) were detected in aortic tissues. The concentration of SO₂ in serum and aortic tissue homogenate supernatant was measured using high-performance liquid chromatography with fluorescence determination. In the in vitro study, VSMC of A7R5 cell lines was divided into six groups: control, AngII, AngII + SO₂, PD98059 (an inhibitor of ERK phosphorylation), AngII + PD98059, and AngII + SO₂ + PD98059. Expression of PCNA, ERK, and P-ERK was determined by Western blotting.

Results:

In animal experiment, compared with the control group, AngII markedly increased blood pressure (P < 0.01) and thickened the aortic wall in mice (P < 0.05) with an increase in the expression of PCNA (P < 0.05). SO₂, however, reduced the systemic hypertension and the wall thickness induced by AngII (P < 0.05). It inhibited the increased expression of PCNA and P-ERK induced by AngII (P < 0.05). In cell experiment, PD98059, an ERK phosphorylation inhibitor, blocked the inhibitory effect of SO₂ on VSMC proliferation (P < 0.05).

Conclusions:

ERK signaling is involved in the mechanisms by which SO₂ inhibits VSMC proliferation in AngII-induced hypertensive mice via ERK signaling.

Unfolded protein response plays a critical role in heart damage after myocardial ischemia/reperfusion in rats

The unfolded protein response (UPR) plays a critical role in cell death mediated by ischemia/reperfusion (I/R) injury. However, little is known about the exact mechanism of UPR signaling pathways after myocardial I/R injury in rats. An attempt was therefore made to assess whether the myocardial I/R induced UPR, and which branch of UPR (ATF6, IRE1 and PERK) signal pathway was activated. Sprague-Dawley rats were pretreated with UPR stimulator dithiothreitol (DTT) and UPR inhibitor 4-phenylbutyrate (4PBA) and then subjected to myocardial I/R surgery. Compared with sham-operated group, the expression of GRP78, ATF6, CHOP and sXBP1 in the I/R injured group is significantly increased at transcript and protein levels, which indicated that all the three signal pathways of UPR were activated in the myocardial I/R injury. Compared with the I/R injured group, treatment with 4PBA effectively decreased myocardium infarct size, reduced myocardial apoptosis, down-regulated caspase-12 expression, diminished serum creatine kinase and lactate dehydrogenase levels. In contrast, these effects were reversed in DTT treated group. In summary, these results demonstrated that myocardial I/R injury activates UPR and inhibiting cell UPR possesses a cardioprotective effect through the suppression of ER stress-induced apoptosis. Therefore, inhibition of UPR might be used as a therapeutic target during myocardial I/R injury.