Endogenous sulfur dioxide regulates hippocampal neuron apoptosis in developing epileptic rats and is associated with the PERK signaling pathway

Small molecule probes as versatile energy acceptors: A breakthrough in photoelectrochemical sensing for sulfur dioxide recording in rat brain

Microelectrode-based photoelectrochemical (PEC) sensing is a newly developed and promising analytical technique for in vivo analysis. However, the inadequate specificity in complex environment of living bodies restricted its further in vivo application. Herein, we utilized a small molecule probe as the energy acceptor to quench the photocurrent of CdTe quantum dots through energy transfer. The efficiency of energy transfer was modulated by the concentration of target SO2, resulting in changes in photocurrent. The chemical recognition reaction between small molecule probes and SO2 enhanced the specificity of PEC sensing, thus guaranteeing its in vivo applications. Furthermore, with the use of light addressing strategy, simultaneous detection in the multiple brain regions was implemented. The energy transfer based light addressable PEC microsensor achieved monitoring fluctuations of SO2 levels in multiple brain regions of rats with epilepsy.

Study of the Impact of Air Pollution on Convulsions in Children: A Hospital-Based Retrospective Study in Hangzhou, China

BACKGROUND

To investigate the relationship between the occurrence of convulsions in children and air pollution in Hangzhou.

METHODS

From January 1, 2018, to December 31, 2020, 775 children admitted with convulsion to the pediatric outpatient clinic of The Affiliated Hospital of Hangzhou Normal University (Hangzhou, China) were enrolled in this study. The clinical data and the corresponding weather data of the day in Hangzhou were collected and analyzed. Also, the monthly etiological classification of convulsions and the monthly average air data of Hangzhou were statistically analyzed.

RESULTS

The highest incidence of convulsion was observed in children 1 to 2 years old, and higher in boys than in girls. The top three main causes were febrile seizure, benign infantile convulsion with mild gastroenteritis, and epilepsy. Among the meteorological factors, the increase in the level of 2.5 micron particulate matter (PM 2.5) in the air per month led to an increase in the number of patients with febrile seizure, benign infantile convulsion with mild gastroenteritis, and epilepsy, where the increase of ozone in 8 hours (O3-8h) per month led to a decrease in the number of patients with such conditions.

CONCLUSIONS

PM2.5, PM10, and SO2 are the main meteorological factors affecting the occurrence of convulsions in children in Hangzhou, and PM2.5 and SO2 are risk factors. The increase in the level of PM2.5 in the air per month could increase occurrence of child convulsions, but the increase of O3-8h per month could decrease occurrence of child convulsions.

Organelle-targeting ratiometric fluorescent probes: design principles, detection mechanisms, bio-applications, and challenges

Biological species, including reactive oxygen species (ROS), reactive sulfur species (RSS), reactive nitrogen species (RNS), F-, Pd2+, Cu2+, Hg2+, and others, are crucial for the healthy functioning of cells in living organisms. However, their aberrant concentration can result in various serious diseases. Therefore, it is essential to monitor biological species in cellular organelles such as the cell membrane, mitochondria, lysosome, endoplasmic reticulum, Golgi apparatus, and nucleus. Among various fluorescent probes for species detection within the organelles, ratiometric fluorescent probes have drawn special attention as a potential way to get beyond the drawbacks of intensity-based probes. This method depends on measuring the intensity change of two emission bands (caused by an analyte), which produces an efficient internal referencing that increases the detection's sensitivity. This review article discusses the literature publications (from 2015 to 2022) on organelle-targeting ratiometric fluorescent probes, the general strategies, the detecting mechanisms, the broad scope, and the challenges currently faced by fluorescent probes.

A Whiff of Sulfur: One Wind a Day Keeps the Doctor Away

Reactive Sulfur Species (RSS), such as allicin from garlic or sulforaphane from broccoli, are fre-quently associated with biological activities and possible health benefits in animals and humans. Among these Organic Sulfur Compounds (OSCs) found in many plants and fungi, the Volatile Sulfur Compounds (VSCs) feature prominently, not only because of their often-pungent smell, but also because they are able to access places which solids and solutions cannot reach that easily. Indeed, inorganic RSS such as hydrogen sulfide (H₂S) and sulfur dioxide (SO₂) can be used to lit-erally fumigate entire rooms and areas. Similarly, metabolites of garlic, such as allyl methyl sulfide (AMS), are formed metabolically in humans in lower concentrations and reach the airways from inside the body as part of one’s breath. Curiously, H₂S is also formed in the gastrointestinal tract by gut bacteria, and the question of if and for which purpose this gas then crosses the barriers and enters the body is indeed a delicate matter for equally delicate studies. In any case, nature is surprisingly rich in such VSCs, as fruits (for instance, the infamous durian) demonstrate, and therefore these VSCs represent a promising group of compounds for further studies.

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 derivatives attenuates consolidation of contextual fear memory in mice

Post-traumatic stress disorder (PTSD) is characterized by an enhancement of traumatic memory. Intervention strategies based on the different stages of memory have been shown to be effective in the prevention and control of PTSD. The endogenous gaseous molecule, sulfur dioxide (SO₂), has been reported to significantly exert neuromodulatory effects; however, its regulation of learning and memory remains unestablished. This study aimed to investigate the effects of exogenous SO₂ derivatives administration on the formation, consolidation, reconsolidation, retention, and expression of contextual fear memory. Behavioral results showed that both intraperitoneal injection (50 mg/kg, ip) and hippocampal infusion (5 μg/side) of SO₂ derivatives (a mixture of sodium sulfite and sodium bisulfite, Na₂SO₃/NaHSO₃, 3:1 M/M) significantly impaired consolidation but had no effect on reconsolidation and retention of contextual fear memory. These findings suggest that the attenuating effects of SO₂ on the consolidation of fear memory involves, at least partially, the region of the hippocampus. The findings of this study provide direct evidence for the development of new strategies for PTSD prevention and treatment involving the use of gaseous SO₂.

A novel fluorescent probe based on triphenylamine for detecting sulfur dioxide derivatives

According to the nucleophilicity of sulfur dioxide derivatives, a reactive fluorescent probe was designed and synthesized by linking triphenylamine with benzoindole.

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.

FRET Modulated Signaling: A Versatile Strategy to Construct Photoelectrochemical Microsensors for In Vivo Analysis

Microelectrode-based electrochemical (EC) and photoelectrochemical (PEC) sensors are promising candidates for in vivo analysis of biologically important chemicals. However, limited selectivity in complicated biological systems and poor adaptability to electrochemically non-active species restrained their applications. Herein, we propose the concept of modulating the PEC output by a fluorescence resonance energy transfer (FRET) process. The emission of energy donor was dependent on the concentration of target SO₂ , which in turn served as the modulator of the photocurrent signal of the photoactive material. The employment of optical modulation circumvented the problem of selectivity, and the as-fabricated PEC microelectrode showed good stability and reproducibility in vivo. It can monitor fluctuations of SO₂ levels in brains of rat models of cerebral ischemia-reperfusion and febrile seizure. More significantly, such a FRET modulated signaling strategy can be extended to diverse analytes.

Exogenous SO2 donor treatment impairs reconsolidation of drug reward memory in mice

Substance-related and addictive disorders (SRADs) are characterized by compulsive drug use and recurrent relapse. The persistence of pathological drug-related memories indisputably contributes to a high propensity to relapse. Hence, strategies to disrupt reconsolidation of drug reward memory are currently being pursued as potential anti-relapse interventions. Sulfur dioxide (SO2), acting as a potential gaseous molecule, endogenously derives from sulfur amino acid and can exert significant neural regulatory effects. However, the role of SO2 in reconsolidation of drug memory has not been determined. In the present study, we used morphine- or cocaine-induced conditioned place preference (CPP) mouse models with retrieval to investigate the effects of exogenous SO2 donor treatment on reconsolidation of drug reward memory. We found that administration of SO2 donor immediately after the retrieval impaired the expression of morphine or cocaine CPP. Furthermore, the exogenous SO2 donor treatment 6 h post-retrieval or in the absence of retrieval had no effect on drug reward memory and the expression of CPP. SO2 itself did not produce aversive effects nor did it acutely block morphine CPP. Our results indicate that exogenous SO2 impairs reconsolidation of drug reward memory rather than inhibits the expression of drug reward memory. As such, SO2 holds potential for the treatment and prevention of SRADs and should be studied further.

Brain Disorders and Chemical Pollutants: A Gap Junction Link?

The incidence of brain pathologies has increased during last decades. Better diagnosis (autism spectrum disorders) and longer life expectancy (Parkinson's disease, Alzheimer's disease) partly explain this increase, while emerging data suggest pollutant exposures as a possible but still underestimated cause of major brain disorders. Taking into account that the brain parenchyma is rich in gap junctions and that most pollutants inhibit their function; brain disorders might be the consequence of gap-junctional alterations due to long-term exposures to pollutants. In this article, this hypothesis is addressed through three complementary aspects: (1) the gap-junctional organization and connexin expression in brain parenchyma and their function; (2) the effect of major pollutants (pesticides, bisphenol A, phthalates, heavy metals, airborne particles, etc.) on gap-junctional and connexin functions; (3) a description of the major brain disorders categorized as neurodevelopmental (autism spectrum disorders, attention deficit hyperactivity disorders, epilepsy), neurobehavioral (migraines, major depressive disorders), neurodegenerative (Parkinson's and Alzheimer's diseases) and cancers (glioma), in which both connexin dysfunction and pollutant involvement have been described. Based on these different aspects, the possible involvement of pollutant-inhibited gap junctions in brain disorders is discussed for prenatal and postnatal exposures.

Mitochondria-targeted polydopamine nanoprobes for visualizing endogenous sulfur dioxide derivatives in a rat epilepsy model

Epilepsy is the fourth most common neurological disorder, and aberrantly elevated sulfur dioxide derivatives (SO₃^2-/HSO₃^-) are thought to underlie the hippocampal neuronal apoptosis in epilepsy. We have designed and synthesized a mitochondria-targeted polydopamine nanoprobe for visualizing endogenous SO₃^2-/HSO₃^- by the nucleophilic addition reaction. The nanoprobe was used for imaging SO₂ derivatives both in the mitochondria of cultured cells and zebrafish, and successfully applied in the hippocampus of a rat model of epilepsy. The PDAD nanoprobe could be of great value for the elucidation of mechanisms of abnormal SO₃^2-/HSO₃^- involved in diseases such as epilepsy.

Development of a unique reversible fluorescent probe for tracking endogenous sulfur dioxide and formaldehyde fluctuation in vivo

A FRET-based reversible fluorescent probe for sensing SO₂ and FA was designed. The probe was first used for imaging endogenous SO₂ and FA in vitro and in vivo. Moreover, we first found that the interaction of SO₂ and FA can reduce the cytotoxicity.

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.