The negative inotropic effects of gaseous sulfur dioxide and its derivatives in the isolated perfused rat heart

Sulfur dioxide increases testosterone biosynthesis by activating ERK1/2 pathway and disrupting autophagy in Leydig cells

Sulfur dioxide (SO2) is a ubiquitous environmental pollutant that has been shown to be toxic to the male reproductive system, but the underlying mechanism remains unclear. Therefore, the SO2-treated mice and primary Leydig cell models were established to investigate the effects of SO2 on the production of testosterone and its specific mechanism. The results demonstrated that SO2 activated the ERK1/2 signaling pathway, leading to increased key proteins expression of testosterone biosynthesis and elevated testosterone levels. The addition of ERK1/2 inhibitor U0126 attenuated SO2-induced increases in key testosterone biosynthetic gene mRNA levels of Star, Cyp17a1, Hsd3b1, and testosterone. Low doses of SO2 reduced the expression of BECLIN1 and LC3 proteins, increased P-4E-BP1 protein expression, and decreased autophagy in Leydig cells. Moreover, increasing doses of SO2 correlate with enhanced Leydig cell autophagy and testosterone levels initially. However, increasing the dose of SO2 resulted in a significant decrease in cell viability and ultimately decreased testosterone levels. These findings suggest that SO2 promotes testosterone production by activating ERK1/2 and disrupting autophagy. This study enriched the dose-effect relationship of SO2 on the male reproductive system and provided a theoretical reference for us to have a comprehensive and dynamic understanding of the SO2 toxic mechanism.

Recent advances in sulfur dioxide releasing nanoplatforms for cancer therapy

Sulfur dioxide (SO2), long considered to be a harmful atmospheric pollutant, has recently been posited as the fourth gasotransmitter, as it is produced endogenously in mammals and has important pathophysiological effects. The field of tumor therapy has witnessed a paradigm shift with the emergence of SO2-based gas therapy. This has been possible because SO2 is a potent glutathione consumer that can promote the production of reactive oxygen species, eventually leading to oxidative-stress-induced cancer cell death. Nevertheless, this therapeutic gas cannot be directly administrated in gaseous form. Thus, various nano formulations incorporating SO2 donors or prodrugs capable of storing and releasing SO2 have been developed in an attempt to achieve active/passive intratumoral accumulation and SO2 release in the tumor microenvironment. In this review article, the advances over the past decade in nanoplatforms incorporating sulfur SO2 prodrugs to provide controlled release of SO2 for cancer therapy are summarized. We first describe the synthesis of polypeptide SO2 prodrugs to overcome multiple drug resistance that was pioneered by our group, followed by other macromolecular SO2 prodrug structures that self-assemble into nanoparticles for tumor therapy. Second, we describe nanoplatforms composed of various small-molecule SO2 donors with endogenous or exogenous stimuli responsiveness, including thiol activated, acid-sensitive, and ultraviolet or near-infrared light-responsive SO2 donors, which have been used for tumor inhibition. Combinations of SO2 gas therapy with photodynamic therapy, chemotherapy, photothermal therapy, sonodynamic therapy, and nanocatalytic tumor therapy are also presented. Finally, we discuss the current limitations and challenges and the future outlook for SO2-based gas therapy. STATEMENT OF SIGNIFICANCE: Gas therapy is attracting increasing attention in the scientific community because it is a highly promising strategy against cancer owing to its inherent biosafety and avoidance of drug resistance. Sulfur dioxide (SO2) is recently found to be produced endogenously in mammals with important pathophysiological effects. This review summarizes recent advances in SO2 releasing nanosystems for cancer therapy, including polymeric prodrugs, endogenous or exogenous stimulus-activated SO2 donors delivered by nanoplatform and combination therapy strategies.

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.

Sulfur Dioxide Derivative Prevents the Prolongation of Action Potential During the Isoproterenol-Induced Hypertrophy of Rat Cardiomyocytes

Exogenous SO2 is toxic especially to the pulmonary and cardiovascular system, similar to nitric-oxide, carbon-monoxide, and hydrogen-sulfide. Endogenous SO2 is produced in many cell types. The SO2 content of the rat heart has been observed to substantially decrease during isoproterenol-induced hypertrophy. This study sought to determine whether an SO2 derivative could inhibit the prolongation of action potentials during the isoproterenol-induced hypertrophy of rat cardiomyocytes and explore the ionic currents. Alongside electrocardiogram recordings, the voltage and current-clamped measurements were conducted in the enzymatically isolated left ventricular cardiomyocytes of Wistar rats. The consistency of the results was evaluated by the novel mathematical electrophysiology model. Our results show that SO2 significantly blocked the prolongation of QT-interval and action potential duration. Furthermore, SO2 did not substantially affect the Na+ currents and did not improve the decreased steady-state and transient outward K+ currents, but it reverted the reduced L-type Ca2+ currents (I CaL) to the physiological levels. Altered inactivation of I CaL was remarkably recovered by SO2. Interestingly, SO2 significantly increased the Ca2+ transients in hypertrophic rat hearts. Our mathematical model also confirmed the mechanism of the SO2 effect. Our findings suggest that the shortening mechanism of SO2 is related to the Ca2+ dependent inactivation kinetics of the Ca2+ current.

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.

Sulfur dioxide induces vascular relaxation through PI3K/Akt/eNOS and NO/cGMP signaling pathways in rats

Sulfur dioxide (SO₂) is a common exogenous atmospheric pollutant. Studies have shown that SO₂ can cause vasodilation as a gas signaling molecule, but the specific signaling pathways are not well understood. This study aimed to explore the underlying mechanism behind the effects of SO₂ on vasodilation of isolated rat aorta. The results showed that when the dose of SO₂ was 30 μM, the vasodilation of endothelium-intact rings was partially suppressed by LY294002 and N^G-nitro-l-arginine methyl ester, and the protein levels of phosphoinositide 3-kinase (PI3K), p-Akt, and p-endothelial nitric oxide synthase (p-eNOS) were significantly increased. When the dose of SO₂ was 300 μM or 1500 μM, the vasodilation of endothelium-denuded rings did not change after application of the inhibitor, but the protein levels of PI3K, p-Akt, and p-eNOS were significantly decreased, and the activity of NOS and the level of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) were significantly increased. We speculate that the mechanism of SO₂-induced vasodilatation likely involved the endothelial PI3K/Akt/eNOS and NO/cGMP signal pathways. In addition, at the concentration of 1500 μM, SO₂ markedly increased the level of caspase-3 and caspase-9. The results suggest that high concentrations of SO₂ may cause damage to blood vessels. This study will help to further inform the etiologies of SO₂-related cardiovascular disease.

Investigating the inotropic effect of pyruvic acid on the isolated rat heart and its underlying mechanism

Pyruvic acid is important organic chemical intermediates that plays a role in cardiomyocyte pathophysiology and therapy. This study sought to explore the inotropic effects of pyruvic acid on the function of the isolated rat hearts and investigate its underlying mechanism. Pyruvic acid produced a greater negative inotropic effect compared to HCl and sodium pyruvate in a concentration-dependent pattern in the hearts. The role of low dose of pyruvic acid on heart function was regulated by pyruvic acid molecules and high dose pyruvic acid may be influenced by pyruvic acid molecules and pH. K_v channels may be involved in the pyruvic acid-induced negative inotropic effect. Finally, pyruvic acid markedly increased the level of LDH and CK and reduced the level of Ca²⁺Mg²⁺-ATPase and Na⁺K⁺-ATPase. These results suggest that pyruvic acid may modulate cardiac function at physiological or low doses but can cause damage to cardiomyocytes at high doses.

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 improves endothelial dysfunction by downregulating the angiotensin II/AT1R pathway in D-galactose-induced aging rats

The aim of this study was to investigate the protective effects of sulfur dioxide (SO₂) on the endothelial function of the aorta in D-galactose (D-gal)-induced aging rats. Sprague Dawley rats were randomized into a D-gal group, a D-gal + SO₂ group and a control group, then injected with D-gal, D-gal + SO₂ donor or equivalent volumes of saline, respectively, for 8 consecutive weeks. After 8 weeks, the mean arterial pressure was significantly increased in the D-gal group, but was lowered by SO₂. SO₂ significantly ameliorated the endothelial dysfunction induced by D-gal treatment. The vasorelaxant effect of SO₂ was associated with the elevated nitric oxide levels and upregulated phosphorylation of endothelial nitric oxide synthase. In the D-gal group, the concentration of angiotensin II in the plasma was significantly increased, but was decreased by SO₂. Moreover, levels of vascular tissue hydrogen peroxide (H₂O₂) and malondialdehyde were significantly lower in SO₂-treated groups than those in the D-gal group. Western blot analysis showed that the expressions of oxidative stress-related proteins (the angiotensin II type 1 receptor (AT₁R), and nicotinamide adenine dinucleotide phosphate oxidase subunits) were increased in the D-gal group, while they were decreased after treatment with SO₂. In conclusion, SO₂ attenuated endothelial dysfunction in association with the inhibition of oxidative stress injury and the downregulation of the angiotensin II/AT₁R pathway in D-gal-induced aging rats.

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.

Chemical trapping and characterization of small oxoacids of sulfur (SOS) generated in aqueous oxidations of H2S

Small oxoacids of sulfur (SOS) are elusive molecules like sulfenic acid, HSOH, and sulfinic acid, HS(O)OH, generated during the oxidation of hydrogen sulfide, H2S, in aqueous solution. Unlike their alkyl homologs, there is a little data on their generation and speciation during H2S oxidation. These SOS may exhibit both nucleophilic and electrophilic reactivity, which we attribute to interconversion between S(II) and S(IV) tautomers. We find that SOS may be trapped in situ by derivatization with nucleophilic and electrophilic trapping agents and then characterized by high resolution LC MS. In this report, we compare SOS formation from H2S oxidation by a variety of biologically relevant oxidants. These SOS appear relatively long lived in aqueous solution, and thus may be involved in the observed physiological effects of H2S.

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.

Sulfur-containing gaseous signal molecules, ion channels and cardiovascular diseases

Sulfur-containing gaseous signal molecules including hydrogen sulphide and sulfur dioxide were previously recognized as toxic gases. However, extensive studies have revealed that they can be generated in the cardiovascular system via a sulfur-containing amino acid metabolic pathway, and have an important role in cardiovascular physiology and pathophysiology. Ion channels are pore-forming membrane proteins present in the membrane of all biological cells; their functions include the establishment of a resting membrane potential and the control of action potentials and other electrical signals by conducting ions across the cell membrane. Evidence has now accumulated suggesting that the sulfur-containing gaseous signal molecules are important regulators of ion channels and transporters. The aims of this review are (1) to discuss the recent experimental evidences in the cardiovascular system regarding the regulatory effects of sulfur-containing gaseous signal molecules on a variety of ion channels, including ATP-sensitive potassium, calcium-activated potassium, voltage-gated potassium, L- and T-type calcium, transient receptor potential and chloride and sodium channels, and (2) to understand how the gaseous signal molecules affect ion channels and cardiovascular diseases.

LINKED ARTICLES

This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.

Benzothiazole Sulfinate: a Water-Soluble and Slow-Releasing Sulfur Dioxide Donor

Sulfur dioxide (SO2) has long been considered a toxic environmental pollutant and byproduct of industrial processing. Recently it has become evident that SO2 may also have regulatory functions in mammalian pulmonary systems. However, the study of these effects has proven to be challenging due to the difficulty in administering SO2 in a reliable manner. In this work, we report the discovery of a new pH-dependent and water-soluble SO2 donor, benzothiazole sulfinate (BTS). We have found BTS to have slow and sustained SO2 release at physiological pH. Additionally, we have explored its vasorelaxation properties as compared to the authentic SO2 gas solutions. The slow release of BTS should make it a useful tool for the study of endogenously generated SO2.

Endogenous Sulfur Dioxide: A New Member of Gasotransmitter Family in the Cardiovascular System

Sulfur dioxide (SO2) was previously regarded as a toxic gas in atmospheric pollutants. But it has been found to be endogenously generated from metabolism of sulfur-containing amino acids in mammals through transamination by aspartate aminotransferase (AAT). SO2 could be produced in cardiovascular tissues catalyzed by its synthase AAT. In recent years, studies revealed that SO2 had physiological effects on the cardiovascular system, including vasorelaxation and cardiac function regulation. In addition, the pathophysiological effects of SO2 were also determined. For example, SO2 ameliorated systemic hypertension and pulmonary hypertension, prevented the development of atherosclerosis, and protected against myocardial ischemia-reperfusion (I/R) injury and isoproterenol-induced myocardial injury. These findings suggested that endogenous SO2 was a novel gasotransmitter in the cardiovascular system and provided a new therapy target for cardiovascular diseases.

The molecular mechanisms of sodium metabisulfite on the expression of K ATP and L-Ca2+ channels in rat hearts

Sodium metabisulfite (SMB) is used as an antioxidant and antimicrobial agent in a variety of drugs and foods. However, there are few reported studies about its side effects. This study is to investigate the SMB effects on the expression of ATP-sensitive K(+) (KATP) and L-type calcium (L-Ca(2+)) channels in rat hearts. The results show that the mRNA and protein levels of the KATP channel subunits Kir6.2 and SUR2A were increased by SMB; on the contrary, SMB at 520 mg/kg significantly decreased the expression of the L-Ca(2+) channel subunits Cav1.2 and Cav1.3. This suggests that SMB can activate the expression of KATP channel by increasing the mRNA and protein levels of Kir6.2 and SUR2A, while it inhibits the expression of L-Ca(2+) channels by decreasing the mRNA and protein levels of Cav1.2 and Cav1.3 in rat hearts. Therefore, the molecular mechanism of the SMB effect on rat hearts might be related to the increased expression of KATP channels and the decreased expression of L-Ca(2+) channels.

Effect of sulfur dioxide inhalation on the expression of KATP and L-Ca(2+) channels in rat hearts

Epidemiological studies have revealed an association between sulfur dioxide (SO2) exposure and cardiovascular diseases. This study is designed to investigate the SO2 effect on the expression of ATP-sensitive K(+) (KATP) channel and L-type calcium (L-Ca(2+)) channel in rat hearts. The results show that the mRNA and protein levels of the KATP channel subunits Kir6.2 and SUR2A of rat hearts in SO2 groups were higher than those in control group. SO2 at 14mg/m(3) significantly decreased the expression of the L-Ca(2+) channel subunits Cav1.2 and Cav1.3. This suggests that SO2 can activate the KATP channels by up-regulating the expression of Kir6.2 and SUR2A, while it inhibits the L-Ca(2+) channels by down-regulating the expression of Cav1.2 and Cav1.3 in rat hearts. The molecular mechanism of SO2-induced negative inotropic effect might be linked to the expression changes of these subunits, which may contribute to the pathogenesis of SO2-associated cardiovascular diseases.

Effects of sodium metabisulfite on the expression of BK(Ca), K(ATP), and L-Ca(2+) channels in rat aortas in vivo and in vitro

Sodium metabisulfite (SMB) is most commonly used as the preservative in many food preparations and drugs. So far, few studies about its negative effects were reported. The purpose of this study was to investigate the effect of SMB on the expression of big-conductance Ca(2+)-activated K(+) (BKCa), ATP-sensitive K(+) (KATP), and L-type calcium (L-Ca(2+)) channels in rat aorta in vivo and in vitro. The results showed that the mRNA and protein levels of the BKCa channel subunits α and β1 of aorta in rats were increased by SMB in vivo and in vitro. Similarly, the expression of the KATP channel subunits Kir6.1, Kir6.2, and SUR2B were increased by SMB. However, SMB at the highest concentration significantly decreased the expression of the L-Ca(2+) channel subunits Cav1.2 and Cav1.3. These results suggest that SMB can activate BKCa and KATP channels by increasing the expression of α, β1, and Kir6.1, Kir6.2, SUR2B respectively, while also inhibit L-Ca(2+) channels by decreasing the expression of Cav1.2 and Cav1.3 of aorta in rats. The molecular mechanism of SMB-induced vasorelaxant effect might be related to the expression changes of BKCa, KATP, and L-Ca(2+) channels subunits. Further work is needed to determine the relative contribution of each channel in SMB-mediated vasorelaxant effect.

Effects of gaseous sulfur dioxide and its derivatives on the expression of KATP, BKCa and L-Ca(2+) channels in rat aortas in vitro

Epidemiological investigations have revealed that sulfur dioxide (SO2) exposure is linked to cardiovascular diseases. Our previous study indicated that the vasorelaxant effect of SO2 might be partly related to ATP-sensitive K(+) (KATP), big-conductance Ca(2+)-activated K(+) (BKCa) and L-type calcium (L-Ca(2+)) channels. The present study was designed to further investigate the effects of gaseous SO2 and its derivatives on the gene and protein expression of these channels in the rat aortas in vitro. The results showed that the mRNA and protein levels of the KATP channel subunits Kir6.1, Kir6.2 and SUR2B of the rat aortas in SO2 and its derivatives groups were higher than those in control group. Similarly, the expression of the BKCa channel subunits α and β1 was increased by SO2 and its derivatives. However, SO2 and its derivatives at 1500μM significantly decreased the expression of the L-Ca(2+) channel subunits Cav1.2 and Cav1.3. Histological examination of the rat aorta tissues showed moderate injury of tunica media induced by SO2 and its derivatives at 1500μM. These results suggest that SO2 and its derivatives can activate the KATP and BKCa channels by increasing the expression of Kir6.1, Kir6.2, SUR2B and α, β1, respectively, while also inhibiting the L-Ca(2+) channels by decreasing the expression of Cav1.2 and Cav1.3 of the rat aortas. The molecular mechanism of the vasorelaxant effect of SO2 and its derivatives might be related to the expression changes of KATP, BKCa and L-Ca(2+) channel subunits, which may play a role in the pathogenesis of SO2-associated cardiovascular diseases.

The role of sulfur dioxide in the regulation of mitochondrion-related cardiomyocyte apoptosis in rats with isopropylarterenol-induced myocardial injury

The authors investigated the regulatory effects of sulfur dioxide (SO₂) on myocardial injury induced by isopropylarterenol (ISO) hydrochloride and its mechanisms. Wistar rats were divided into four groups: control group, ISO group, ISO plus SO₂ group, and SO₂ only group. Cardiac function was measured and cardiomyocyte apoptosis was detected. Bcl-2, bax and cytochrome c (cytc) expressions, and caspase-9 and caspase-3 activities in the left ventricular tissues were examined in the rats. The opening status of myocardial mitochondrial permeability transition pore (MPTP) and membrane potential were analyzed. The results showed that ISO-treated rats developed heart dysfunction and cardiac injury. Furthermore, cardiomyocyte apoptosis in the left ventricular tissues was augmented, left ventricular tissue bcl-2 expression was down-regulated, bax expression was up-regulated, mitochondrial membrane potential was significantly reduced, MPTP opened, cytc release from mitochondrion into cytoplasm was significantly increased, and both caspase-9 and caspase-3 activities were increased. Administration of an SO₂ donor, however, markedly improved heart function and relieved myocardial injury of the ISO-treated rats; it lessened cardiomyocyte apoptosis, up-regulated myocardial bcl-2, down-regulated bax expression, stimulated mitochondrial membrane potential, closed MPTP, and reduced cytc release as well as caspase-9 and caspase-3 activities in the left ventricular tissue. Hence, SO₂ attenuated myocardial injury in association with the inhibition of apoptosis in myocardial tissues, and the bcl-2/cytc/caspase-9/caspase-3 pathway was possibly involved in this process.

Sulfur dioxide preconditioning increases antioxidative capacity in rat with myocardial ischemia reperfusion (I/R) injury

BACKGROUND

The study was designed to explore if sulfur dioxide (SO2) preconditioning increased antioxidative capacity in rat with myocardial ischemia reperfusion (I/R) injury.

METHODS

The myocardial I/R model was made by left coronary artery ligation for 30min and reperfusion for 120min in rats. Myocardial infarct size and plasma lactate dehydrogenase (LDH) and creatine kinase (CK) activities, plasma superoxide dismutase (SOD), malondialdehyde (MDA), glutathione peroxidase (GSH-Px) and glutathione (GSH) changes were detected for the rats. The contents of myocardial hydrogen sulfide (H2S) and nitric oxide (NO) were measured. Myocardial protein expressions of SOD1, SOD2, cystathionine γ-lyase (CSE) and iNOS were tested using Western blot.

RESULTS

Myocardial infarction developed and plasma CK and LDH activities were significantly increased in I/R group compared with those in control group, but SO2 preconditioning significantly reduced myocardial infarct size, and plasma CK and LDH activities. SO2 preconditioning successfully increased plasma SOD, GSH and GSH-Px levels and myocardial SOD1 protein expression, but decreased MDA level in rats of I/R group. Compared with controls, the myocardial H2S level and CSE expression were decreased after I/R, but myocardial NO level and iNOS expression were increased. With the treatment of SO2, myocardial H2S level and CSE expression were increased, but myocardial NO level and iNOS expression were decreased compared with those in I/R group.

CONCLUSIONS

SO2 preconditioning could significantly reduce I/R-induced myocardial injury in vivo in association with increased myocardial antioxidative capacity, upregulated myocardial H2S/CSE pathway but downregulated NO/iNOS pathway.

The PI3K/Akt pathway mediates the protection of SO(2) preconditioning against myocardial ischemia/reperfusion injury in rats

AIM

To explore the mechanisms underlying the protection by SO2 preconditioning against rat myocardial ischemia/reperfusion (I/R) injury.

METHODS

Male Wistar rats underwent 30-min left coronary artery ligation followed by 120-min reperfusion. An SO2 donor (1 μmol/kg) was intravenously injected 10 min before the ischemia, while LY294002 (0.3 mg/kg) was intravenously injected 30 min before the ischemia. Plasma activities of LDH and CK were measured with an automatic enzyme analyzer. Myocardial infarct size was detected using Evans-TTC method. The activities of caspase-3 and -9 in myocardium were assayed using a commercial kit, and the levels of p-Akt, Akt, PI3K and p-PI3K were examined with Western blotting.

RESULTS

Pretreatment with SO2 significantly reduced the myocardial infarct size and plasma LDH and CK activities, as well as myocardial caspase-3 and -9 activities in the rats. Furthermore, the pretreatment significantly increased the expression levels of myocardial p-Akt and p-PI3K p85. Administration of the PI3K inhibitor LY294002 blocked all the effects induced by SO2 pretreatment.

CONCLUSION

The results suggest that the PI3K/Akt pathway mediates the protective effects of SO2 preconditioning against myocardial I/R injury in rats.