Dynamic Change of Hydrogen Sulfide After Traumatic Brain Injury and its Effect in Mice

Dynamic Changes and Effects of H2S, IGF-1, and GH in the Traumatic Brain Injury

The aim of this study was to examine the expression changes of H2S, IGF-1, and GH in traumatic brain injury (TBI) patients and to detect their neuroprotective functions after TBI. In this study, we first collected cerebrospinal fluid (CSF) and plasma from TBI patients at different times after injury and evaluated the concentrations of H2S, IGF-1, and GH. In vitro studies were using the scratch-induced injury model and cell-cell interaction model (HT22 hippocampal neurons co-cultured with LPS-induced BV2 microglia cells). In vivo studies were using the controlled cortical impact (CCI) model in mice. Cell viability was assessed by CCK-8 assay. Pro-inflammatory cytokines expression was determined by qRT-PCR, ELISA, and nitric oxide production. Western blot was performed to assess the expression of CBS, CSE, IGF-1, and GHRH. Moreover, the recovery of TBI mice was evaluated for behavioral function by applying the modified Neurological Severity Score (mNSS), the Rotarod test, and the Morris water maze. We discovered that serum H2S, CSF H2S, and serum IGF-1 concentrations were all adversely associated with the severity of the TBI, while the concentrations of IGF-1 and GH in CSF and GH in the serum were all positively related to TBI severity. Experiments in vitro and in vivo indicated that treatment with NaHS (H2S donor), IGF-1, and MR-409 (GHRH agonist) showed protective effects after TBI. This study gives novel information on the functions of H2S, IGF-1, and GH in TBI.

The Role of Hydrogen Sulfide in the Localization and Expression of p53 and Cell Death in the Nervous Tissue in Traumatic Brain Injury and Axotomy

Traumatic brain injury (TBI) is one of the leading causes of disability and death worldwide. It is characterized by various molecular-cellular events, with the main ones being apoptosis and damage to axons. To date, there are no clinically effective neuroprotective drugs. In this study, we examined the role of hydrogen sulfide (H2S) in the localization and expression of the key pro-apoptotic protein p53, as well as cell death in the nervous tissue in TBI and axotomy. We used a fast donor (sodium sulphide, Na2S) H2S and a classic inhibitor (aminooxyacetic acid, AOAA) of cystathionine β-synthase (CBS), which is a key enzyme in H2S synthesis. These studies were carried out on three models of neurotrauma in vertebrates and invertebrates. As a result, it was found that Na2S exhibits a pronounced neuroprotective effect that reduces the number of TUNEL-positive neurons and glial cells in TBI and apoptotic glia in axotomy. This effect could be realized through the Na2S-dependent decrease in the level of p53 in the cells of the nervous tissue of vertebrates and invertebrates, which we observed in our study. We also observed the opposite effect when using AOAA, which indicates the important role of CBS in the regulation of p53 expression and death of neurons and glial cells in TBI and axotomy.

Cystathionine β-Synthase Suppresses NLRP3 Inflammasome Activation via Redox Regulation in Microglia

Aims: Cystathionine β-synthase (CBS) is essential for homocysteine (Hcy) transsulfuration, yielding cysteine as a common precursor of hydrogen sulfide (H2S), glutathione (GSH), and other sulfur molecules, which produce neuroprotective effects in neurological conditions. We previously reported a disruption of microglial CBS/H2S signaling in a Parkinson's disease (PD) mouse model. Yet, it remains unclear whether CBS affects nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing 3 (NLRP3) inflammasome activity and other pathologies in PD. Results: Microglial CBS expression decreased after lipopolysaccharide (LPS) stimulation. Elevated GSSG (the oxidized GSH) content and decreased H2S generation were found in the brains of microglial cbs conditional-knockout (cbscKO) mice, whereas serum and brain Hcy levels remained unaltered. Moreover, microglial cbscKO mice were susceptible to NLRP3 inflammasome activation and dopaminergic neuron losses caused by LPS injection into the substantia nigra, whereas cbs overexpression or activation produced opposite effects. In vitro studies showed that cbs overexpression or activation suppressed microglial NLRP3 inflammasome activation and interleukin (IL)-1β secretion by reducing mitochondrial reactive oxygen species (mitoROS) level. Conversely, ablation of cbs enhanced NLRP3 expression and mitoROS generation and augmented microglial NLRP3 inflammasome activity in response to adenosine triphosphate challenge, which was blocked by the mitoROS scavenger. Innovation and Conclusion: The study demonstrated an elevated GSSG level and reduced H2S generation, which correlated with a susceptible status of microglia in the brain of cbscKO mice. Our findings reveal a critical role of CBS in restraining the microglial NLRP3 inflammasome by controlling redox homeostasis and highlight that activation or upregulation of CBS may become a potential strategy for PD treatment.

The Role of Hydrogen Sulfide in Regulation of Cell Death following Neurotrauma and Related Neurodegenerative and Psychiatric Diseases

Injuries of the central (CNS) and peripheral nervous system (PNS) are a serious problem of the modern healthcare system. The situation is complicated by the lack of clinically effective neuroprotective drugs that can protect damaged neurons and glial cells from death. In addition, people who have undergone neurotrauma often develop mental disorders and neurodegenerative diseases that worsen the quality of life up to severe disability and death. Hydrogen sulfide (H₂S) is a gaseous signaling molecule that performs various cellular functions in normal and pathological conditions. However, the role of H₂S in neurotrauma and mental disorders remains unexplored and sometimes controversial. In this large-scale review study, we examined the various biological effects of H₂S associated with survival and cell death in trauma to the brain, spinal cord, and PNS, and the signaling mechanisms underlying the pathogenesis of mental illnesses, such as cognitive impairment, encephalopathy, depression and anxiety disorders, epilepsy and chronic pain. We also studied the role of H₂S in the pathogenesis of neurodegenerative diseases: Alzheimer's disease (AD) and Parkinson's disease (PD). In addition, we reviewed the current state of the art study of H₂S donors as neuroprotectors and the possibility of their therapeutic uses in medicine. Our study showed that H₂S has great neuroprotective potential. H₂S reduces oxidative stress, lipid peroxidation, and neuroinflammation; inhibits processes associated with apoptosis, autophagy, ferroptosis and pyroptosis; prevents the destruction of the blood-brain barrier; increases the expression of neurotrophic factors; and models the activity of Ca²⁺ channels in neurotrauma. In addition, H₂S activates neuroprotective signaling pathways in psychiatric and neurodegenerative diseases. However, high levels of H₂S can cause cytotoxic effects. Thus, the development of H₂S-associated neuroprotectors seems to be especially relevant. However, so far, all H₂S modulators are at the stage of preclinical trials. Nevertheless, many of them show a high neuroprotective effect in various animal models of neurotrauma and related disorders. Despite the fact that our review is very extensive and detailed, it is well structured right down to the conclusions, which will allow researchers to quickly find the proper information they are interested in.

Hydrogen sulfide signalling in neurodegenerative diseases

The gaseous neurotransmitter hydrogen sulfide (H2 S) exerts neuroprotective efficacy in the brain via post-translational modification of cysteine residues by sulfhydration, also known as persulfidation. This process is comparable in biological impact to phosphorylation and mediates a variety of signalling events. Unlike conventional neurotransmitters, H2 S cannot be stored in vesicles due to its gaseous nature. Instead, it is either locally synthesized or released from endogenous stores. Sulfhydration affords both specific and general neuroprotective effects and is critically diminished in several neurodegenerative disorders. Conversely, some forms of neurodegenerative disease are linked to excessive cellular H2 S. Here, we review the signalling roles of H2 S across the spectrum of neurodegenerative diseases, including Huntington's disease, Parkinson's disease, Alzheimer's disease, Down syndrome, traumatic brain injury, the ataxias, and amyotrophic lateral sclerosis, as well as neurodegeneration generally associated with ageing.

Protective Roles of Hydrogen Sulfide in Alzheimer's Disease and Traumatic Brain Injury

The gaseous signaling molecule hydrogen sulfide (H₂S) critically modulates a plethora of physiological processes across evolutionary boundaries. These include responses to stress and other neuromodulatory effects that are typically dysregulated in aging, disease, and injury. H₂S has a particularly prominent role in modulating neuronal health and survival under both normal and pathologic conditions. Although toxic and even fatal at very high concentrations, emerging evidence has also revealed a pronounced neuroprotective role for lower doses of endogenously generated or exogenously administered H₂S. Unlike traditional neurotransmitters, H₂S is a gas and, therefore, is unable to be stored in vesicles for targeted delivery. Instead, it exerts its physiologic effects through the persulfidation/sulfhydration of target proteins on reactive cysteine residues. Here, we review the latest discoveries on the neuroprotective roles of H₂S in Alzheimer's disease (AD) and traumatic brain injury, which is one the greatest risk factors for AD.

Elamipretide mitigates ischemia-reperfusion injury in a swine model of hemorrhagic shock

ischemia-reperfusion injury (IRI) after hemorrhage is potentiated by aortic occlusion or resuscitative endovascular balloon occlusion of the aorta (REBOA). Given the central role of mitochondrial injury in shock, we hypothesized that Elamipretide, a peptide that protects mitochondria, would mitigate IRI after hemorrhagic shock and REBOA. Twelve pigs were subjected to hemorrhagic shock and 45 min of REBOA. After 25 min of REBOA, animals received either saline or Elamipretide. Animals were transfused with autologous blood during balloon deflation, and pigs were resuscitated with isotonic crystalloids and norepinephrine for 4.25 h. Elamipretide-treated animals required less crystalloids than the controls (62.5 [50-90] and 25 [5-30] mL/kg, respectively), but similar amounts of norepinephrine (24.7 [8.6-39.3] and 9.7 [2.1-12.5] mcg/kg, respectively). Treatment animals had a significant reduction in serum creatinine (control: 2.7 [2.6-2.8]; Elamipretide: 2.4 [2.4-2.5] mg/dL; p = 0.04), troponin (control: 3.20 [2.14-5.47] ng/mL, Elamipretide: 0.22 [0.1-1.91] ng/mL; p = 0.03), and interleukin-6 concentrations at the end of the study. There were no differences in final plasma lactate concentration. Elamipretide reduced fluid requirements and protected the kidney and heart after profound IRI. Further understanding the subcellular consequences of REBOA and mitochondrial rescue will open new therapeutic avenues for patients suffering from IRI after hemorrhage.

H2S-based fluorescent imaging for pathophysiological processes

Hydrogen sulfide (H₂S), as an important endogenous signaling molecule, plays a vital role in many physiological processes. The abnormal behaviors of hydrogen sulfide in organisms may lead to various pathophysiological processes. Monitoring the changes in hydrogen sulfide is helpful for pre-warning and treating these pathophysiological processes. Fluorescence imaging techniques can be used to observe changes in the concentration of analytes in organisms in real-time. Therefore, employing fluorescent probes imaging to investigate the behaviors of hydrogen sulfide in pathophysiological processes is vital. This paper reviews the design strategy and sensing mechanisms of hydrogen sulfide-based fluorescent probes, focusing on imaging applications in various pathophysiological processes, including neurodegenerative diseases, inflammation, apoptosis, oxidative stress, organ injury, and diabetes. This review not only demonstrates the specific value of hydrogen sulfide fluorescent probes in preclinical studies but also illuminates the potential application in clinical diagnostics.

Gut-Brain cross talk: The pathogenesis of neurodevelopmental impairment in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating condition of multi-factorial origin that affects the intestine of premature infants and results in high morbidity and mortality. Infants that survive contend with several long-term sequelae including neurodevelopmental impairment (NDI)-which encompasses cognitive and psychosocial deficits as well as motor, vision, and hearing impairment. Alterations in the gut-brain axis (GBA) homeostasis have been implicated in the pathogenesis of NEC and the development of NDI. The crosstalk along the GBA suggests that microbial dysbiosis and subsequent bowel injury can initiate systemic inflammation which is followed by pathogenic signaling cascades with multiple pathways that ultimately lead to the brain. These signals reach the brain and activate an inflammatory cascade in the brain resulting in white matter injury, impaired myelination, delayed head growth, and eventual downstream NDI. The purpose of this review is to summarize the NDI seen in NEC, discuss what is known about the GBA, explore the relationship between the GBA and perinatal brain injury in the setting of NEC, and finally, highlight the existing research into possible therapies to help prevent these deleterious outcomes.

Surface-fill H2S-releasing silk fibroin hydrogel for brain repair through the repression of neuronal pyroptosis

Traumatic brain injury (TBI) remains the major cause of disability and mortality worldwide due to the persistent neuroinflammation and neuronal death induced by TBI. Among them, pyroptosis, a specific type of programmed cell death (PCD) triggered by inflammatory signals, plays a significant part in the pathological process after TBI. Inhibition of neuroinflammation and pyroptosis is considered a possible strategy for the treatment of TBI. In our previous study, exogenous hydrogen sulfide(H₂S) exerted a neuroprotective effect after TBI. Here, we developed a surface-fill H₂S-releasing silk fibroin (SF) hydrogel (H₂S@SF hydrogel) to achieve small-dose local administration and avoid volatile and toxic side effects. We used a controlled cortical impact (CCI) to establish a mild TBI model in mice to examine the effect of H₂S@SF hydrogel on TBI-induced pyroptosis. We found that H₂S@SF hydrogel inhibited the expression of H₂S synthase in neurons after TBI and significantly inhibited TBI-induced neuronal pyroptosis. In addition, immunofluorescence staining results showed that the necroptosis protein receptor-interacting serine/threonine-protein kinase 1 (RIPK1) partially colocalized with the pyroptosis protein Gasdermin D (GSDMD) in the same cells. H₂S@SF hydrogel can also inhibit the expression of the necroptosis protein. Moreover, H₂S@SF hydrogel also alleviates brain edema and the degree of neurodegeneration in the acute phase of TBI. The neuroprotective effect of H₂S@SF hydrogel was further confirmed by wire-grip test, open field test, Morris water maze, beam balance test, radial arm maze, tail suspension, and forced swimming test. Lastly, we also measured spared tissue volume, reactive astrocytes and activated microglia to demonstrate H₂S@SF hydrogel impacts on long-term prognosis in TBI. Our study provides a new theoretical basis for the treatment of H₂S after TBI and the clinical application of H₂S@SF hydrogel. STATEMENT OF SIGNIFICANCE: Silk fibroin (SF) hydrogel controls the release of hydrogen sulfide (H₂S) to inhibit neuronal pyroptosis and neuroinflammation in injured brain tissue. In this study, we synthesized a surface-fill H₂S-releasing silk fibroin hydrogel, which could slowly release H₂S to reshape the homeostasis of endogenous H₂S in injured neurons and inhibit neuronal pyroptosis in a mouse model of traumatic brain injury. Meanwhile, H₂S@SF hydrogel could alleviate brain edema and the degree of neurodegeneration, improve motor dysfunction, anxious behavior and memory impairment caused by TBI, reduce tissue loss and ameliorate neuroinflammation. Our study provides a new theoretical basis for the treatment of H₂S after TBI and the clinical application of H₂S@SF hydrogel.

Targeting hydrogen sulfide and nitric oxide to repair cardiovascular injury after trauma

The systemic cardiovascular effects of major trauma, especially neurotrauma, contribute to death and permanent disability in trauma patients and treatments are needed to improve outcomes. In some trauma patients, dysfunction of the autonomic nervous system produces a state of adrenergic overstimulation, causing either a sustained elevation in catecholamines (sympathetic storm) or oscillating bursts of paroxysmal sympathetic hyperactivity. Trauma can also activate innate immune responses that release cytokines and damage-associated molecular patterns into the circulation. This combination of altered autonomic nervous system function and widespread systemic inflammation produces secondary cardiovascular injury, including hypertension, damage to cardiac tissue, vascular endothelial dysfunction, coagulopathy and multiorgan failure. The gasotransmitters nitric oxide (NO) and hydrogen sulfide (H2S) are small gaseous molecules with potent effects on vascular tone regulation. Exogenous NO (inhaled) has potential therapeutic benefit in cardio-cerebrovascular diseases, but limited data suggests potential efficacy in traumatic brain injury (TBI). H2S is a modulator of NO signaling and autonomic nervous system function that has also been used as a drug for cardio-cerebrovascular diseases. The inhaled gases NO and H2S are potential treatments to restore cardio-cerebrovascular function in the post-trauma period.

Hydrogen sulfide prevents the vascular dysfunction induced by severe traumatic brain injury in rats by reducing reactive oxygen species and modulating eNOS and H2S-synthesizing enzyme expression

AIM

To assess the effects of subchronic administration with NaHS, an exogenous H₂S donor, on TBI-induced hypertension and vascular impairments.

MAIN METHODS

Animals underweministration does not prevent the body weight loss but slightly imnt a lateral fluid percussion injury, and the hemodynamic variables were measured in vivo by plethysmograph method. The vascular function in vitro, the ROS levels by the DCFH-DA method and the expression of H₂S-synthesizing enzymes and eNOS by Western blot were measured in isolated thoracic aortas at day 7 post-TBI. The effect of L-NAME on NaHS-induced effects in vascular function was evaluated. Brain water content was determined 7 days after trauma induction. Body weight was recorded throughout the experimental protocol, whereas the sensorimotor function was evaluated using the neuroscore test at days -1 (basal), 2, and 7 after the TBI induction.

KEY FINDINGS

TBI animals showed: 1) an increase in hemodynamic variables and ROS levels in aortas; 2) vascular dysfunction; 3) sensorimotor dysfunction; and 4) a decrease in body weight, the expression of H₂S-synthesizing enzymes, and eNOS phosphorylation. Interestingly, NaHS subchronic administration (3.1 mg/kg; i.p.; every 24 h for six days) prevented the development of hypertension, vascular dysfunction, and oxidative stress. L-NAME abolished NaHS-induced effects. Furthermore, NaHS treatment restored H₂S-synthesizing enzymes and eNOS phosphorylation with no effect on body weight, sensorimotor impairments, or brain water content.

SIGNIFICANCE

Taken together, these results demonstrate that H₂S prevents TBI-induced hypertension by restoring vascular function and modulating ROS levels, H₂S-synthesizing enzymes expression, and eNOS phosphorylation.

Hydrogen sulfide poisoning in forensic pathology and toxicology: mechanism and metabolites quantification analysis

Historically, hydrogen sulfide (H₂S) poisoning has extremely high and irreparable mortality. Currently, the identification of H₂S poisoning needs to combine with the case scene analysis in forensic medicine. The anatomy of the deceased seldom had obvious features. There are also a few reports about H₂S poisoning in detail. As a result, we give a comprehensive analysis of the related knowledge on the forensic aspect of H₂S poisoning. Furthermore, we provide the analytical methods of H₂S and its metabolite-which may assist in H₂S poisoning identification.

Exogenous hydrogen sulfide restores CSE and CBS but no 3-MST protein expression in the hypothalamus and brainstem after severe traumatic brain injury

Hydrogen sulfide (H₂S) is a gasotransmitter endogenously synthesized by cystathionine-γ-lyase (CSE), cystathionine-β-synthase (CBS), and 3-mercaptopiruvate sulfurtransferase (3-MST) enzymes. H₂S exogenous administration prevents the development of hemodynamic impairments after traumatic brain injury (TBI). Since the hypothalamus and the brainstem highly regulate the cardiovascular system, this study aimed to evaluate the effect of NaHS subchronic treatment on the changes of H₂S-sythesizing enzymes in those brain areas after TBI and in physiological conditions. For that purpose, animals were submitted to a lateral fluid percussion injury, and the changes in CBS, CSE, and 3-MST protein expression were measured by western blot at days 1, 2, 3, 7, and 28 in the vehicle group, and 7 and 28 days after NaHS treatment. After severe TBI induction, we found a decrease in CBS and CSE protein expression in the hypothalamus and brainstem; meanwhile, 3-MST protein expression diminished only in the hypothalamus compared to the Sham group. Remarkably, i.p. daily injections of NaHS, an H₂S donor, (3.1 mg/kg) during seven days: (1) restored CBS and CSE but no 3-MST protein expression in the hypothalamus at day 28 post-TBI; (2) reestablished only CSE in brainstem 7 and 28 days after TBI; and (3) did not modify H₂S-sythesizing enzymes protein expression in uninjured animals. Mainly, our results show that the NaHS effect on CBS and CSE protein expression is observed in a time- and tissue-dependent manner with no effect on 3-MST expression, which may suggest a potential role of H₂S synthesis in hypothalamus and brainstem impairments observed after TBI.

Role of hydrogen sulfide in subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a common acute and severe disease worldwide, which imposes a heavy burden on families and society. However, the current therapeutic strategies for SAH are unsatisfactory. Hydrogen sulfide (H2 S), as the third gas signaling molecule after carbon monoxide and nitric oxide, has been widely studied recently. There is growing evidence that H2 S has a promising future in the treatment of central nervous system diseases. In this review, we focus on the effects of H2 S in experimental SAH and elucidate the underlying mechanisms. We demonstrate that H2 S has neuroprotective effects and significantly reduces secondary damage caused by SAH via antioxidant, antiinflammatory, and antiapoptosis mechanisms, and by alleviating cerebral edema and vasospasm. Based on these findings, we believe that H2 S has great potential in the treatment of SAH and warrants further study to promote its early clinical application.

Endovascular Perfusion Augmentation for Critical Care Decreases Vasopressor Requirements while Maintaining Renal Perfusion

BACKGROUND

Ischemia reperfusion injury causes a profound hyperdynamic distributive shock. Endovascular perfusion augmentation for critical care (EPACC) has emerged as a hemodynamic adjunct to vasopressors and crystalloid. The objective of this study was to examine varying levels of mechanical support for the treatment of ischemiareperfusion injury in swine.

METHODS

Fifteen swine underwent anesthesia and then a controlled 30% blood volume hemorrhage followed by 30 min of supra-celiac aortic occlusion to create an ischemia-reperfusion injury Animals were randomized to standardized critical care (SCC), EPACC with low threshold (EPACC-Low), and EPACC with high threshold (EPACC-High). The intervention phase lasted 270 min after injury Hemodynamic markers and laboratory values of ischemia were recorded.

RESULTS

During the intervention phase, SCC spent 82.4% of the time avoiding proximal hypotension (>60 mm Hg), while EPACC-Low spent 97.6% and EPACC-High spent 99.5% of the time avoiding proximal hypotension, P  < 0.001. Renal artery flow was statistically increased in EPACC-Low compared with SCC (2.29 mL/min/kg vs. 1.77 mL/ min/kg, P  < 0.001), while renal flow for EPACC-High was statistically decreased compared with SCC (1.25 mL/min/kg vs. 1.77 mL/min/kg, P  < 0.001). EPACC animals required less intravenous norepinephrine, (EPACC-Low: 16.23mcg/kg and EPACC-High: 13.72 mcg/kg), compared with SCC (59.45 mcg/kg), P = 0.049 and P = 0.013 respectively.

CONCLUSIONS

Compared with SCC, EPACC-High and EPACC-Low had decreased norepinephrine requirements with decreased frequency of proximal hypotension. EPACC-Low paradoxically had increased renal perfusion despite having a mechanical resistor in the aorta proximal to the renal arteries. This is the first description of low volume mechanical hemodynamic support in the setting of profound shock from ischemia-reperfusion injury in swine demonstrating stabilized proximal hemodynamics and augmented distal perfusion.

Biological Connection of Psychological Stress and Polytrauma under Intensive Care: The Role of Oxytocin and Hydrogen Sulfide

This paper explored the potential mediating role of hydrogen sulfide (H2S) and the oxytocin (OT) systems in hemorrhagic shock (HS) and/or traumatic brain injury (TBI). Morbidity and mortality after trauma mainly depend on the presence of HS and/or TBI. Rapid "repayment of the O2 debt" and prevention of brain tissue hypoxia are cornerstones of the management of both HS and TBI. Restoring tissue perfusion, however, generates an ischemia/reperfusion (I/R) injury due to the formation of reactive oxygen (ROS) and nitrogen (RNS) species. Moreover, pre-existing-medical-conditions (PEMC's) can aggravate the occurrence and severity of complications after trauma. In addition to the "classic" chronic diseases (of cardiovascular or metabolic origin), there is growing awareness of psychological PEMC's, e.g., early life stress (ELS) increases the predisposition to develop post-traumatic-stress-disorder (PTSD) and trauma patients with TBI show a significantly higher incidence of PTSD than patients without TBI. In fact, ELS is known to contribute to the developmental origins of cardiovascular disease. The neurotransmitter H2S is not only essential for the neuroendocrine stress response, but is also a promising therapeutic target in the prevention of chronic diseases induced by ELS. The neuroendocrine hormone OT has fundamental importance for brain development and social behavior, and, thus, is implicated in resilience or vulnerability to traumatic events. OT and H2S have been shown to interact in physical and psychological trauma and could, thus, be therapeutic targets to mitigate the acute post-traumatic effects of chronic PEMC's. OT and H2S both share anti-inflammatory, anti-oxidant, and vasoactive properties; through the reperfusion injury salvage kinase (RISK) pathway, where their signaling mechanisms converge, they act via the regulation of nitric oxide (NO).

Hydrogen Sulfide Subchronic Treatment Improves Hypertension Induced by Traumatic Brain Injury in Rats through Vasopressor Sympathetic Outflow Inhibition

Traumatic brain injury (TBI) represents a critical public health problem around the world. To date, there are no accurate therapeutic approaches for the management of cardiovascular impairments induce by TBI. In this regard, hydrogen sulfide (H₂S), a novel gasotransmitter, has been proposed as a neuro- and cardioprotective molecule. This study was designed to determine the effect of subchronic management with sodium hydrosulfide (NaHS) on hemodynamic, vasopressor sympathetic outflow and sensorimotor alterations produced by TBI. Animals underwent a lateral fluid percussion injury, and changes in hemodynamic variables were measured by pletismographic methods. In addition, vasopressor sympathetic outflow was assessed by a pithed rat model. Last, sensorimotor impairments were evaluated by neuroscore test and beam-walking test. At seven, 14, 21, and 28 days after moderate-severe TBI, the animals showed: (1) a decrease on sensorimotor function in the neuroscore test and beam-walking test; (2) an increase in heart rate, systolic, diastolic, and mean blood pressure; (3) progressive sympathetic hyperactivity; and (4) a decrease in vasopressor responses induced by noradrenaline (α_1/2-adrenoceptors agonist) and UK 14,304 (selective α₂-adrenoceptor agonist). Interestingly, intraperitoneal daily injections of NaHS, an H₂S donor (3.1 and 5.6 mg/kg), during seven days after TBI prevented the development of the impairments in hemodynamic variables, which were similar to those obtained in sham animals. Moreover, NaHS treatment prevented the sympathetic hyperactivity and decreased noradrenaline-induced vasopressor responses. No effects on sensorimotor dysfunction were observed, however. Taken together, our results suggest that H₂S ameliorates the hemodynamic and sympathetic system impairments observed after TBI.

Mechanical Brain Injury Increases Cells' Production of Cystathionine β-Synthase and Glutamine Synthetase, but Reduces Pax2 Expression in the Telencephalon of Juvenile Chum Salmon, Oncorhynchus keta

The considerable post-traumatic brain recovery in fishes makes them a useful model for studying the mechanisms that provide reparative neurogenesis, which is poorly represented in mammals. After a mechanical injury to the telencephalon in adult fish, lost neurons are actively replaced due to the proliferative activity of neuroepithelial cells and radial glia in the neurogenic periventricular zone. However, it is not enough clear which signaling mechanisms are involved in the activation of adult neural stem cells (aNSC) after the injury (reactive proliferation) and in the production of new neurons (regenerative neurogenesis) from progenitor cells (NPC). In juvenile Pacific salmon, the predominant type of NSCs in the telencephalon are neuroepithelial cells corresponding to embryonic NSCs. Expression of glutamine synthetase (GS), a NSC molecular marker, was detected in the neuroepithelial cells of the pallium and subpallium of juvenile chum salmon, Oncorhynchus keta. At 3 days after a traumatic brain injury (TBI) in juvenile chum salmon, the GS expression was detected in the radial glia corresponding to aNSC in the pallium and subpallium. The maximum density of distribution of GS⁺ radial glia was found in the dorsal pallial region. Hydrogen sulfide (H₂S) is a proneurogenic factor that reduces oxidative stress and excitotoxicity effects, along with the increased GS production in the brain cells of juvenile chum salmon. In the fish brain, H₂S producing by cystathionine β-synthase in neurogenic zones may be involved in maintaining the microenvironment that provides optimal conditions for the functioning of neurogenic niches during constitutive neurogenesis. After injury, H₂S can determine cell survivability, providing a neuroprotective effect in the area of injury and reducing the process of glutamate excitotoxicity, acting as a signaling molecule involved in changing the neurogenic environment, which leads to the reactivation of neurogenic niches and cell regeneration programs. The results of studies on the control of the expression of regulatory Sonic Hedgehog genes (Shh) and the transcription factors Paired Box2 (Pax2) regulated by them are still insufficient. A comparative analysis of Pax2 expression in the telencephalon of intact chum salmon showed the presence of constitutive patterns of Pax2 expression in neurogenic areas and non-neurogenic parenchymal zones of the pallium and subpallium. After mechanical injury, the patterns of Pax2 expression changed, and the amount of Pax2⁺ decreased (p < 0.05) in lateral (Dl), medial (Dm) zones of the pallium, and the lateral zone (Vl) of the subpallium compared to the control. We believe that the decrease in the expression of Pax2 may be caused by the inhibitory effect of the Pax6 transcription factor, whose expression in the juvenile salmon brain increases upon injury.

Biologic Effect of Hydrogen Sulfide and Its Role in Traumatic Brain Injury

Ever since endogenous hydrogen sulfide (H₂S) was found in mammals in 1989, accumulated evidence has demonstrated that H₂S functions as a novel neurological gasotransmitter in brain tissues and may play a key role in traumatic brain injury. It has been proved that H₂S has an antioxidant, anti-inflammatory, and antiapoptosis function in the neuron system and functions as a neuroprotective factor against secondary brain injury. In addition, H₂S has other biologic effects such as regulating the intracellular concentration of Ca²⁺, facilitating hippocampal long-term potentiation (LTP), and activating ATP-sensitive K channels. Due to the toxic nature of H₂S when exceeding the physiological dose in the human body, only a small amount of H₂S-related therapies was applied to clinical treatment. Therefore, it has huge therapeutic potential and has great hope for recovering patients with traumatic brain injury.

Hydrogen sulfide protects against cell damage through modulation of PI3K/Akt/Nrf2 signaling

Hydrogen sulfide as the third endogenous gaseous mediator had protective effects against traumatic brain injury-induced neuronal damage in mice. However, the exact pathophysiological mechanism underlying traumatic brain injury is complicated and the protective role of H₂S is not yet fully known. Therefore, we combined the mechanical injury (scratch) with secondary injury including metabolic impairment (no glucose) together to investigate the underlying cellular mechanism of hydrogen sulfide in vitro models of traumatic brain injury. In the present study, we found that H₂S could prevent the scratch-induced decrease in the expression of cystathionine-β-synthetase, a key enzyme involved in the source of hydrogen sulfide, and endogenous hydrogen sulfide generation in PC12 cells. We also found that hydrogen sulfide could prevent scratch-induced cellular injury, alteration of mitochondrial membrane potential, intracellular accumulation of reactive oxygen species and cell death (autophagic cell death and apoptosis) in PC12 cells. It was also found that blocking PI3K/AKT pathway by LY294002, abolished the protection of H₂S against scratch-induced cellular reactive oxygen species level and NRF2 accumulation and function in the nucleus. These results suggest that hydrogen sulfide protects against cell damage induced by scratch injury through modulation of the PI3K/Akt/Nrf2 pathway. This study raises the possibility that hydrogen sulfide may have therapeutic efficacy in traumatic brain injury.

Gas-Mediated Cancer Bioimaging and Therapy

Gas-involving cancer theranostics have attracted considerable attention in recent years due to their high therapeutic efficacy and biosafety. We have reviewed the recent significant advances in the development of stimuli-responsive gas releasing molecules (GRMs) and gas nanogenerators for cancer bioimaging, targeted and controlled gas therapy, and gas-sensitized synergistic therapy. We have focused on gases with known anticancer effects, such as oxygen (O₂), carbon monoxide (CO), nitric oxide (NO), hydrogen sulfide (H₂S), hydrogen (H₂), sulfur dioxide (SO₂), carbon dioxide (CO₂), and heavy gases that act via the gas-generating process. The GRMs and gas nanogenerators for each gas have been described in terms of the stimulation method, followed by their applications in ultrasound and multimodal imaging, and finally their primary and synergistic actions with other cancer therapeutic modalities. The current challenges and future possibilities of gas therapy and imaging vis-à-vis clinical translation have also been discussed.

Exogenous Hydrogen Sulfide Offers Neuroprotection on Intracerebral Hemorrhage Injury Through Modulating Endogenous H2S Metabolism in Mice

Hydrogen sulfide (H₂S), an important endogenous signaling molecule, has a significant neuroprotective role in the central nervous system. In this study, we examined the protective effects of exogenous H₂S against intracerebral hemorrhage (ICH), as well as its underlying mechanisms. We investigated the effects of exogenous H₂S on ICH using Western blotting, injury volume, measurement of brain edema, propidium iodide (PI) staining, and behavior assessment, respectively. We found that endogenous H₂S production was downregulated in the brain after ICH, which is caused by the decrease in cystathionine β-synthase (CBS) as the predominant cerebral H₂S-generating enzyme in the brain. Treatment with sodium hydrosulfide (NaHS; an H₂S producer) could restore the H₂S production and the expression of CBS. NaHS could also attenuate brain edema, injury volume, and neurological deficits in the Morris water maze test after ICH. Western blotting results indicated that H₂S pretreatment reversed the increase in caspase 3 cleavage and the decrease in Bcl-2, suppressed the activation of autophagy marker (LC3II and Beclin-1), and maintained the p62 level in injured striatum post-ICH. However, H₂S could not restore brain CBS expression and H₂S content, reduce brain edema, and improve motor performance and memory function after ICH through modulating autophagy and apoptosis when pretreated with the CBS inhibitor aminooxyacetic acid (AOAA). We also found that AOAA reduced the endogenous H₂S production through inhibiting the enzyme activity of CBS rather than modulating the expression of CBS protein level. These present results indicate that H₂S may possess potential therapeutic value in the treatment of brain injury after ICH, and the protective effect of exogenous H₂S against ICH may be not a direct action but an indirect effect through inducing endogenous H₂S metabolism responses.

H2S attenuates sepsis-induced cardiac dysfunction via a PI3K/Akt-dependent mechanism

The heart is the most vulnerable target organ in sepsis, and it has been previously reported that hydrogen sulfide (H₂S) has a protective role in heart dysfunction caused by sepsis. Additionally, studies have demonstrated that the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt) signaling pathway has a protective function during sepsis. However, the potential association between H₂S and PI3K/Akt in sepsis-induced cardiac dysfunction is unclear. Therefore, the PI3K inhibitor LY294002 was used to investigate the role of PI3K/Akt signaling in the protective effects of H₂S during sepsis-induced myocardial injury. A rat sepsis model was established using cecal ligation and puncture (CLP) surgery. Sodium hydrosulfide, a H₂S donor, was administered intraperitoneally (8.9 µmol/kg), and serum myocardial enzyme levels, inflammatory cytokine levels, cardiac histology and cardiomyocyte apoptosis were assessed to determine the extent of myocardial damage. The results demonstrated that exogenous H₂S reduced serum myocardial enzyme levels, decreased the levels of the inflammatory factors tumor necrosis factor (TNF)-α and interleukin (IL)-6, and increased the level of anti-inflammatory IL-10 following CLP. Staining of histological sections demonstrated that myocardial damage and cardiomyocyte apoptosis were alleviated by the administration of exogenous H₂S. Western blot analysis was used to detect phosphorylated and total PI3K and Akt levels, as well as NF-κB, B-cell lymphoma-2, Bcl-2-associated X protein (Bax) and caspase levels, and the results demonstrated that H₂S significantly increased PI3K and Akt phosphorylation. This indicated that the PI3K/Akt signaling pathway was activated by H₂S. Additionally, H₂S reduced Bax and caspase expression, indicating that apoptosis was inhibited, and decreased NF-κB levels, indicating that inflammation was reduced. Furthermore, the PI3K inhibitor LY294002 eliminated the protective effects of H₂S. In conclusion, the results of the current study suggest that exogenous H₂S activates PI3K/Akt signaling to attenuate myocardial damage in sepsis.

Characterization and Biological Activity of a Hydrogen Sulfide-Releasing Red Light-Activated Ruthenium(II) Complex

Hydrogen sulfide (H₂S) is a biological gasotransmitter that has been employed for the treatment of ischemia-reperfusion injury. Despite its therapeutic value, the implementation of this gaseous molecule for this purpose has required H₂S-releasing prodrugs for effective intracellular delivery. The majority of these prodrugs, however, spontaneously release H₂S via uncontrolled hydrolysis. Here, we describe a Ru(II)-based H₂S-releasing agent that can be activated selectively by red light irradiation. This compound operates in living cells, increasing intracellular H₂S concentration only upon irradiation with red light. Furthermore, the red light irradiation of this compound protects H9c2 cardiomyoblasts from an in vitro model of ischemia-reperfusion injury. These results validate the use of red light-activated H₂S-releasing agents as valuable tools for studying the biology and therapeutic utility of this gasotransmitter.

The Impact of Uremic Toxins on Cerebrovascular and Cognitive Disorders

Individuals at all stages of chronic kidney disease (CKD) have a higher risk of developing cognitive disorders and dementia. Stroke is also highly prevalent in this population and is associated with a higher risk of neurological deterioration, in-hospital mortality, and poor functional outcomes. Evidence from in vitro studies and in vivo animal experiments suggests that accumulation of uremic toxins may contribute to the pathogenesis of stroke and amplify vascular damage, leading to cognitive disorders and dementia. This review summarizes current evidence on the mechanisms by which uremic toxins may favour the occurrence of cerebrovascular diseases and neurological complications in CKD.

The Role of Gaseous Molecules in Traumatic Brain Injury: An Updated Review

Traumatic brain injury (TBI) affects millions of people in China each year. TBI has a high mortality and often times a serious prognosis. The causative mechanisms of TBI during development and recovery from an injury remain vague, leaving challenges for the medical community to provide treatment options that improve prognosis and provide an optimal recovery. Biological gaseous molecules including nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide (H₂S), and molecular hydrogen (H₂) have been found to play critical roles in physiological and pathological conditions in mammals. Accumulating evidence has found that these gaseous molecules can execute neuroprotection in many central nervous system (CNS) conditions due to their highly permeable properties allowing them to enter the brain. Considering the complicated mechanisms and the serious prognosis of TBI, effective and adequate therapeutic approaches are urgently needed. These four gaseous molecules can be potential attractive therapeutic intervention on TBI. In this review, we will present a comprehensive overview on the role of these four biological gasses in the development of TBI and their potential therapeutic applications.

Hydrogen sulfide, nitric oxide, and neurodegenerative disorders

Hydrogen Sulfide (H2S) and Nitric Oxide (NO) have become recognized as important gaseous signaling molecules with enormous pharmacological effects, therapeutic value, and central physiological roles. NO is one of the most important regulators of the pathophysiological condition in central nervous system (CNS). It is critical in the various functioning of the brain; however, beyond certain concentration/level, it is toxic. H2S was regarded as toxic gas with the smell like rotten egg. But, it is now regarded as emerging neuroprotectant and neuromodulator. Recently, the use of donors and inhibitors of these signaling molecules have helped us to identify their accurate and precise biological effects. The most abundant neurotransmitter of CNS (glutamate) is the initiator of the reaction that forms NO, and H2S is highly expressed in brain. These molecules are shedding light on the pathogenesis of various neurological disorders. This review is mainly focused on the importance of H2S and NO for normal functioning of CNS.

Neuroprotective effects of hydrogen sulfide on sodium azide-induced oxidative stress in PC12 cells

Alzheimer's disease (AD) is the most common neurodegenerative disorder, responsible for >50% of all dementia cases. Sodium azide (NaN₃) inhibits cytochrome oxidase by irreversibly binding to the heme cofactor and selectively reducing the complex IV activity, which is present in post-mortem AD brains. Previous data demonstrated that hydrogen sulfide (H₂S), the third endogenous gaseous mediator, exerted protective effects against neuronal damage. Therefore, it was hypothesized that H₂S may be able to scavenge excess reactive oxygen species (ROS), thereby protecting against oxidative stress and cell death. In the present study, it was observed that cell viability decreased in a concentration-dependent manner 12 h after NaN₃ treatment (20, 30 and 50 mmol/l). A decrease in cell viability (to 51±3%) was observed 12 h after treatment with 30 mM NaN₃. NaN₃ treatment also led to decreased mitochondrial membrane potential, increased lipid peroxidation (excessive production of malondialdehyde), and increased the protein expression levels of caspase-3. Pretreatment with H₂S (200 μmol/l) attenuated NaN₃-mediated apoptosis, and the anti-apoptotic action of H₂S was partially dependent on suppressing the production of ROS. The findings of the present study suggested that H₂S exerted a neuroprotective effect against NaN₃-induced neurotoxicity through mechanisms related to anti-oxidation and anti-apoptosis. Therefore, the findings of the present study suggest there may be a promising future for H₂S-based preventions and therapies for neuronal damage following exposure to NaN₃.

Hydrogen sulfide therapy in brain diseases: from bench to bedside

Hydrogen sulfide (H₂S) has been recognized and studied for nearly 300 years, but past researches mainly focus on its toxicity effect. During the past two decades, the majority of researches have reported that H₂S is a novel endogenous gaseous signal molecule in organisms, and play an important role in various systems and diseases. H₂S is mainly produced by three enzymes, including cystathionine β-synthase, cystathionine γ-lyase and 3-mercaptopyruvate sulfurtransferase along with cysteine aminotransferase. H₂S had been firstly reported as a neuromodulator in the brain, because of its essential role in the facilitating hippocampal long-term potentiation at physiological concentration. It is subsequently reported that H₂S may have relevance to neurologic disorders through antioxidative, anti-inflammatory, anti-apoptotic and additional effects. Recent basic medical studies and preclinical studies on neurologic diseases have demonstrated that the administration of H₂S at physiological or pharmacological levels attenuates brain injury. However, the neuroprotective effect of H₂S is concentration-dependent, only a comparatively low dose of H₂S can provide beneficial effect. Herein, we review the neuroprotevtive role of H₂S therapy in brain diseases from its mechanism to clinical application in animal and human subjects, and therefore provide the potential strategies for further clinical treatment.

Metabolomics of trauma-associated death: shared and fluid-specific features of human plasma vs lymph

BACKGROUND

Water-soluble components in mesenteric lymph have been implicated in the pathophysiology of acute lung injury and distal organ failure following trauma and haemorrhagic shock. Proteomics analyses have recently shown similarities and specificities of post-trauma/haemorrhagic shock lymph and plasma. We hypothesise that the metabolic phenotype of post-trauma/haemorrhagic shock mesenteric lymph and plasma share common metabolites, but are also characterised by unique features that differentiate these two fluids.

MATERIALS AND METHODS

Matched samples were collected from 5 brain-dead organ donors who had suffered extreme trauma/haemorrhagic shock. Metabolomics analyses were performed through ultra-high performance liquid chromatography mass spectrometry.

RESULTS

Overall, 269 metabolites were identified in either fluid. Despite significant overlapping, metabolic phenotypes of matched lymph or plasma from the same patients could be used to discriminate sample fluid or biological patient/traumatic-injury origin. Metabolites showing relatively high levels in both fluids included markers of haemolysis and cell lysis secondary to tissue injury.

DISCUSSION

High positive correlations were observed between the quantitative levels of markers of systemic metabolic derangement following traumatic/haemorrhagic hypoxaemia, such as succinate, oxoproline, urate and fatty acids. These metabolites might contribute to coagulopathies of trauma and neutrophil priming driving acute lung injury. Future studies will investigate whether the observed compositional specificities mirror functional or pathological adaptations after trauma and haemorrhage.

bFGF Protects Against Blood-Brain Barrier Damage Through Junction Protein Regulation via PI3K-Akt-Rac1 Pathway Following Traumatic Brain Injury

Many traumatic brain injury (TBI) survivors sustain neurological disability and cognitive impairments due to the lack of defined therapies to reduce TBI-induced blood-brain barrier (BBB) breakdown. Exogenous basic fibroblast growth factor (bFGF) has been shown to have neuroprotective function in brain injury. The present study therefore investigates the beneficial effects of bFGF on the BBB after TBI and the underlying mechanisms. In this study, we demonstrate that bFGF reduces neurofunctional deficits and preserves BBB integrity in a mouse model of TBI. bFGF suppresses RhoA and upregulates tight junction proteins, thereby mitigating BBB breakdown. In vitro, bFGF exerts a protective effect on BBB by upregulating tight junction proteins claudin-5, occludin, zonula occludens-1, p120-catenin, and β-catenin under oxygen glucose deprivation/reoxygenation (OGD) in human brain microvascular endothelial cells (HBMECs). Both the in vivo and in vitro effects are related to the activation of the downstream signaling pathway, PI3K/Akt/Rac-1. Inhibition of the PI3K/Akt or Rac-1 by specific inhibitors LY294002 or si-Rac-1, respectively, partially reduces the protective effect of bFGF on BBB integrity. Overall, our results indicate that the protective role of bFGF on BBB involves the regulation of tight junction proteins and RhoA in the TBI model and OGD-induced HBMECs injury, and that activation of the PI3K/Akt /Rac-1 signaling pathway underlies these effects.

Hydrogen sulfide improves neural function in rats following cardiopulmonary resuscitation

The alleviation of brain injury is a key issue following cardiopulmonary resuscitation (CPR). Hydrogen sulfide (H₂S) is hypothesized to be involved in the pathophysiological process of ischemia-reperfusion injury, and exerts a protective effect on neurons. The aim of the present study was to investigate the effects of H₂S on neural functions following cardiac arrest (CA) in rats. A total of 60 rats were allocated at random into three groups. CA was induced to establish the model and CPR was performed after 6 min. Subsequently, sodium hydrosulfide (NaHS), hydroxylamine or saline was administered to the rats. Serum levels of H₂S, neuron-specific enolase (NSE) and S100β were determined following CPR. In addition, neurological deficit scoring (NDS), the beam walking test (BWT), prehensile traction test and Morris water maze experiment were conducted. Neuronal apoptosis rates were detected in the hippocampal region following sacrifice. After CPR, as the H₂S levels increased or decreased, the serum NSE and S100β concentrations decreased or increased, respectively (P<0.0w. The NDS results of the NaHS group were improved compared with those of the hydroxylamine group at 24 h after CPR (P<0.05). In the Morris water maze experiment, BWT and prehensile traction test the animals in the NaHS group performed best and rats in the hydroxylamine group performed worst. At day 7, the apoptotic index and the expression of caspase-3 were reduced in the hippocampal CA1 region, while the expression of Bcl-2 increased in the NaHS group; and results of the hydroxylamine group were in contrast. Therefore, the results of the present study indicate that H₂S is able to improve neural function in rats following CPR.

Administration of NaHS Attenuates Footshock-Induced Pathologies and Emotional and Cognitive Dysfunction in Triple Transgenic Alzheimer's Mice

Alzheimer's disease (AD) is characterized by progressive cognitive decline and neuropsychiatric symptoms. Increasing evidence indicates that environmental risk factors in young adults may accelerate cognitive loss in AD and that Hydrogen Sulfide (H2S) may represent an innovative treatment to slow the progression of AD. Therefore, the aim of this study was to evaluate the effects of NaHS, an H2S donor, in a triple transgenic AD mouse model (3×Tg-AD) under footshock with situational reminders (SRs). Inescapable footshock with SRs induced anxiety and cognitive dysfunction as well as a decrease in the levels of plasma H2S and GSH and an increase in IL-6 levels in 3×Tg-AD mice. Under footshock with SR stimulus, amyloid deposition, tau protein hyperphosphorylation, and microgliosis were highly increased in the stress-responsive brain structures, including the hippocampus and amygdala, of the AD mice. Oxidative stress, inflammatory response, and β-site APP cleaving enzyme 1 (BACE1) levels were also increased, and the level of inactivated glycogen synthase kinase-3β (GSK3β) (pSer9) was decreased in the hippocampi of AD mice subjected to footshock with SRs. Furthermore, the numbers of cholinergic neurons in the medial septum/diagonal band of Broca (MS/DB) and noradrenergic neurons in the locus coeruleus (LC) were also decreased in the 3×Tg-AD mice under footshock with SRs. These biochemical hallmarks and pathological presentations were all alleviated by the semi-acute administration of NaHS in the AD mice. Together, these findings suggest that footshock with SRs induces the impairment of spatial cognition and emotion, which involve pathological changes in the peripheral and central systems, including the hippocampus, MS/DB, LC, and BLA, and that the administration of NaHS may be a candidate strategy to ameliorate the progression of neurodegeneration.

Development of a Clinically Applicable Protocol for Assessment of Hypoxic Response Through Measurement of the Endogenous Gasotransmitter Hydrogen Sulfide in Human Plasma

BACKGROUND

Gasotransmitters are endogenously made, biologically active gases with unique physiological properties. In addition to participation in the hypoxic respiratory reflex of the carotid body, the gasotransmitter hydrogen sulfide (H(2)S) is thought to play a role in more localized vasodilatory hypoxic tissue responses. This pilot project describes a methodology suitable to the clinical environment that allows for H(2)S gas capture in human plasma utilizing the fluorescent trapping agent dansyl azide.

METHODS

Under an IRB-approved pilot project, 10 healthy male volunteers were spontaneously ventilated on room air, hypoxic (15% oxygen, 85% nitrogen), and hyperoxic (100%) gas mixtures through a nonrebreather system. Venous whole-blood samples were collected at both internal jugular and antecubital sites following 7 minutes of exposure to the tested oxygen environments. Resultant plasma aliquots were treated with dansyl azide and submitted to fluorescence reading (excitation 340 nm, emission 517 nm).

RESULTS

Compiled mean data from volunteer plasma samples demonstrated statistically significant findings (P<0.05) in measurement of increased fluorescent intensity between those samples collected under mildly hypoxic conditions compared with normoxic and hyperoxic samples submitted to the same laboratory criteria.

CONCLUSIONS

To study the role of H(2)S as a marker of hypoxic response in humans, a reliable, robust, and safe protocol amenable to standard hospital laboratory procedures is needed. Through modification to methodologies described in the biochemistry literature, this pilot project demonstrates the feasibility of utilizing a fluorescent H2S gas trapping agent for assessment of hypoxic response in humans within the confines of a typical clinical collection and analysis environment.

Hydrogen sulfide: a neuromodulator and neuroprotectant in the central nervous system

Hydrogen sulfide (H2S) used to be known as a toxic gas. However, in the last two decades, accumulating evidence has revealed its role as a bioactive molecule in the biological systems. H2S has relatively high expression in the brain, exerting multiple functions in both health and diseases. It modulates neurotransmission by influencing behaviors of NMDA receptors and second messenger systems including intracellular Ca(2+) concentration and intracellular cAMP levels and so forth. H2S shows potential therapeutic value in several CNS diseases including Alzheimer's disease, Parkinson's disease, ischemic stroke, and traumatic brain injury. As a neuroprotectant, H2S produces antioxidant, anti-inflammatory, and antiapoptotic effects in pathological situations. Sulfhydration of target proteins is an important mechanism underlying these effects. This Review summarizes the current understanding of H2S in the central nervous system, with emphasis on its role as a neuromodulator and a neuroprotectant.

Hydrogen sulphide increases hepatic differentiation of human tooth pulp stem cells compared with human bone marrow stem cells

AIM

To determine the differences in stem cell properties, in hepatic differentiation and in the effects of hydrogen sulphide (H2 S) on hepatic differentiation between human bone marrow stem cells (hBMC) and stem cells from human exfoliated primary tooth pulp (SHED).

METHODOLOGY

CD117(+) cells were magnetically separated and subjected to hepatic differentiation. CD117(+) cell lineages were characterized for transcription factors indicative of stem cells by qRT-PCR. For the last 9 days of the differentiation, the test cells were exposed to 0.1 ng mL(-1) H2 S. Immunocytochemistry and flow cytometry of albumin, alpha-fetoprotein and carbamoyl phosphate synthetase were carried out after differentiation. Urea concentration and glycogen synthesis were also determined.

RESULTS

Genes expressed in SHED were also expressed in BMC. No difference in expression level of hepatic markers was shown by immunofluorescence. SHED showed more positive cells than hBMC (P < 0.01). H2 S increased the number of positive cells in both cultures (P < 0.01). Urea concentration and glycogen synthesis increased significantly after H2 S exposure (P < 0.001 and P < 0.05, respectively). Real-time PCR data were analysed by RT(2) profiler RT-PCR Array Data Analysis version 3.5 (Qiagen), and ELISA data were analysed by Bonferroni's multiple comparison using Windows spss version 16 (SPSS Inc, Chicago, IL, USA). Bonferroni's multiple comparison test was also carried out after angle transformation for the percentage data of flow cytometer using Windows spss(®) version 16 (SPSS Inc). Statistical significance was accepted at P < 0.05.

CONCLUSIONS

Stem cells from human exfoliated primary tooth pulp and BMC have similar properties. The level of hepatic differentiation in SHED compared with BMC was the same or higher. H2 S increased the level of hepatic differentiation.

Hydrogen sulfide offers neuroprotection on traumatic brain injury in parallel with reduced apoptosis and autophagy in mice

Hydrogen sulfide (H₂S), a novel gaseous mediator, has been recognized as an important neuromodulator and neuroprotective agent in the central nervous system. The present study was undertaken to study the effects of exogenous H₂S on traumatic brain injury (TBI) and the underlying mechanisms. The effects of exogenous H₂S on TBI were examined by using measurement of brain edema, behavior assessment, propidium iodide (PI) staining, and Western blotting, respectively. Compared to TBI groups, H₂S pretreatment had reduced brain edema, improved motor performance and ameliorated performance in Morris water maze test after TBI. Immunoblotting results showed that H₂S pretreatment reversed TBI-induced cleavage of caspase-3 and decline of Bcl-2, suppressed LC3-II, Beclin-1 and Vps34 activation and maintained p62 level in injured cortex and hippocampus post TBI. The results suggest a protective effect and therapeutic potential of H₂S in the treatment of brain injury and the protective effect against TBI may be associated with regulating apoptosis and autophagy.