Cardiovascular disease and resuscitated septic shock lead to the downregulation of the H2S-producing enzyme cystathionine-γ-lyase in the porcine coronary artery

Sulfide regulation of cardiovascular function in health and disease

Hydrogen sulfide (H2S) has emerged as a gaseous signalling molecule with crucial implications for cardiovascular health. H2S is involved in many biological functions, including interactions with nitric oxide, activation of molecular signalling cascades, post-translational modifications and redox regulation. Various preclinical and clinical studies have shown that H2S and its synthesizing enzymes - cystathionine γ-lyase, cystathionine β-synthase and 3-mercaptosulfotransferase - can protect against cardiovascular pathologies, including arrhythmias, atherosclerosis, heart failure, myocardial infarction and ischaemia-reperfusion injury. The bioavailability of H2S and its metabolites, such as hydropersulfides and polysulfides, is substantially reduced in cardiovascular disease and has been associated with single-nucleotide polymorphisms in H2S synthesis enzymes. In this Review, we highlight the role of H2S, its synthesizing enzymes and metabolites, their roles in the cardiovascular system, and their involvement in cardiovascular disease and associated pathologies. We also discuss the latest clinical findings from the field and outline areas for future study.

The effect of targeted hyperoxemia in a randomized controlled trial employing a long-term resuscitated, model of combined acute subdural hematoma and hemorrhagic shock in swine with coronary artery disease: An exploratory, hypothesis-generating study

Controversial evidence is available regarding suitable targets for the arterial O₂ tension (P_aO₂) after traumatic brain injury and/or hemorrhagic shock (HS). We previously demonstrated that hyperoxia during resuscitation from hemorrhagic shock attenuated cardiac injury and renal dysfunction in swine with coronary artery disease. Therefore, this study investigated the impact of targeted hyperoxemia in a long-term, resuscitated model of combined acute subdural hematoma (ASDH)-induced brain injury and HS. The prospective randomized, controlled, resuscitated animal investigation consisted of 15 adult pigs. Combined ASDH plus HS was induced by injection of 0.1 ml/kg autologous blood into the subdural space followed by controlled passive removal of blood. Two hours later, resuscitation was initiated comprising re-transfusion of shed blood, fluids, continuous i.v. noradrenaline, and either hyperoxemia (target P_aO₂ 200 – 250 mmHg) or normoxemia (target P_aO₂ 80 – 120 mmHg) during the first 24 h of the total of 54 h of intensive care. Systemic hemodynamics, intracranial and cerebral perfusion pressures, parameters of brain microdialysis and blood biomarkers of brain injury did not significantly differ between the two groups. According to the experimental protocol, P_aO₂ was significantly higher in the hyperoxemia group at the end of the intervention period, i.e., at 24 h of resuscitation, which coincided with a higher brain tissue PO₂. The latter persisted until the end of observation period. While neurological function as assessed using the veterinary Modified Glasgow Coma Score progressively deteriorated in the control group, it remained unaffected in the hyperoxemia animals, however, without significant intergroup difference. Survival times did not significantly differ in the hyperoxemia and control groups either. Despite being associated with higher brain tissue PO₂ levels, which were sustained beyond the intervention period, targeted hyperoxemia exerted neither significantly beneficial nor deleterious effects after combined ASDH and HS in swine with pre-existing coronary artery disease. The unavailability of a power calculation and, thus, the limited number of animals included, are the limitations of the study.

Brain Histology and Immunohistochemistry After Resuscitation From Hemorrhagic Shock in Swine With Pre-Existing Atherosclerosis and Sodium Thiosulfate (Na2S2O3) Treatment

Background

The hydrogen sulfide (H₂S) and the oxytocin/oxytocin receptor (OT/OTR) systems interact in the central nervous and cardiovascular system. As a consequence of osmotic balance stress, H₂S stimulates OT release from the paraventricular nuclei (PVN) in the hypothalamic regulation of blood volume and pressure. Hemorrhagic shock (HS) represents one of the most pronounced acute changes in blood volume, which, moreover, may cause at least transient brain tissue hypoxia. Atherosclerosis is associated with reduced vascular expression of the main endogenous H₂S producing enzyme cystathionine-γ-lyase (CSE), and, hence, exogenous H₂S administration could be beneficial in these patients, in particular after HS. However, so far cerebral effects of systemic H₂S administration are poorly understood. Having previously shown lung-protective effects of therapeutic Na₂S₂O₃ administration in a clinically relevant, long-term, porcine model of HS and resuscitation we evaluated if these protective effects were extended to the brain.

Methods

In this study, available unanalyzed paraffin embedded brain sections (Na₂S₂O₃N = 8 or vehicle N = 5) of our recently published HS study were analyzed via neuro-histopathology and immunohistochemistry for the endogenous H₂S producing enzymes, OT, OTR, and markers for brain injury and oxidative stress (glial fibrillary acidic protein (GFAP) and nitrotyrosine).

Results

Neuro-histopathological analysis revealed uninjured brain tissue with minor white matter edema. Protein quantification in the hypothalamic PVN showed no significant inter-group differences between vehicle or Na₂S₂O₃ treatment.

Conclusions

The endogenous H₂S enzymes, OT/OTR co-localized in magnocellular neurons in the hypothalamus, which may reflect their interaction in response to HS-induced hypovolemia. The preserved blood brain barrier (BBB) may have resulted in impermeability for Na₂S₂O₃ and no inter-group differences in the PVN. Nonetheless, our results do not preclude that Na₂S₂O₃ could have a therapeutic benefit in the brain in an injury that disrupts the BBB, e.g., traumatic brain injury (TBI) or acute subdural hematoma (ASDH).

The H2S Donor Sodium Thiosulfate (Na2S2O3) Does Not Improve Inflammation and Organ Damage After Hemorrhagic Shock in Cardiovascular Healthy Swine

We previously demonstrated marked lung-protective properties of the H2S donor sodium thiosulfate (Na2S2O3, STS) in a blinded, randomized, controlled, long-term, resuscitated porcine model of swine with coronary artery disease, i.e., with decreased expression of the H2S-producing enzyme cystathionine-γ-lyase (CSE). We confirmed these beneficial effects of STS by attenuation of lung, liver and kidney injury in mice with genetic CSE deletion (CSE-ko) undergoing trauma-and-hemorrhage and subsequent intensive care-based resuscitation. However, we had previously also shown that any possible efficacy of a therapeutic intervention in shock states depends both on the severity of shock as well as on the presence or absence of chronic underlying co-morbidity. Therefore, this prospective, randomized, controlled, blinded experimental study investigated the effects of the STS in cardiovascular healthy swine. After anesthesia and surgical instrumentation, 17 adult Bretoncelles-Meishan-Willebrand pigs were subjected to 3 hours of hemorrhage by removal of 30% of the blood volume and titration of the mean arterial pressure (MAP) ≈ 40 ± 5 mmHg. Afterwards, the animals received standardized resuscitation including re-transfusion of shed blood, fluids, and, if needed, continuous i.v. noradrenaline to maintain MAP at pre-shock values. Animals were randomly allocated to either receive Na2S2O3 or vehicle control starting 2 hours after initiation of shock until 24 hours of resuscitation. The administration of Na2S2O3 did not alter survival during the observation period of 68 hours after the initiation of shock. No differences in cardio-circulatory functions were noted despite a significantly higher cardiac output, which coincided with significantly more pronounced lactic acidosis at 24 hours of resuscitation in the Na2S2O3 group. Parameters of liver, lung, and kidney function and injury were similar in both groups. However, urine output was significantly higher in the Na2S2O3 group at 24 hours of treatment. Taken together, this study reports no beneficial effect of Na2S2O3 in a clinically relevant model of hemorrhagic shock-and-resuscitation in animals without underlying chronic cardiovascular co-morbidity.

Effects of Sodium Thiosulfate During Resuscitation From Trauma-and-Hemorrhage in Cystathionine-γ-Lyase Knockout Mice With Diabetes Type 1

Background

Sodium thiosulfate (STS) is a recognized drug with antioxidant and H2S releasing properties. We recently showed that STS attenuated organ dysfunction and injury during resuscitation from trauma-and-hemorrhage in CSE-ko mice, confirming its previously described organ-protective and anti-inflammatory properties. The role of H2S in diabetes mellitus type 1 (DMT1) is controversial: genetic DMT1 impairs H2S biosynthesis, which has been referred to contribute to endothelial dysfunction and cardiomyopathy. In contrast, development and severity of hyperglycemia in streptozotocin(STZ)-induced DMT1 was attenuated in CSE-ko mice. Therefore, we tested the hypothesis whether STS would also exert organ-protective effects in CSE-ko mice with STZ-induced DMT1, similar to our findings in animals without underlying co-morbidity.

Methods

Under short-term anesthesia with sevoflurane and analgesia with buprenorphine CSE-ko mice underwent DMT1-induction by single STZ injection (100 μg⋅g-1). Seven days later, animals underwent blast wave-induced blunt chest trauma and surgical instrumentation followed by 1 h of hemorrhagic shock (MAP 35 ± 5 mmHg). Resuscitation comprised re-transfusion of shed blood, lung-protective mechanical ventilation, fluid resuscitation and continuous i.v. norepinephrine together with either i.v. STS (0.45 mg⋅g-1) or vehicle (n = 9 in each group). Lung mechanics, hemodynamics, gas exchange, acid-base status, stable isotope-based metabolism, and visceral organ function were assessed. Blood and organs were collected for analysis of cytokines, chemokines, and immunoblotting.

Results

Diabetes mellitus type 1 was associated with more severe circulatory shock when compared to our previous study using the same experimental design in CSE-ko mice without co-morbidity. STS did not exert any beneficial therapeutic effect. Most of the parameters measured of the inflammatory response nor the tissue expression of marker proteins of the stress response were affected either.

Conclusion

In contrast to our previous findings in CSE-ko mice without underlying co-morbidity, STS did not exert any beneficial therapeutic effect in mice with STZ-induced DMT1, possibly due to DMT1-related more severe circulatory shock. This result highlights the translational importance of both integrating standard ICU procedures and investigating underlying co-morbidity in animal models of shock research.

H2S in Critical Illness—A New Horizon for Sodium Thiosulfate?

Ever since the discovery of endogenous H₂S and the identification of its cytoprotective properties, efforts have been made to develop strategies to use H₂S as a therapeutic agent. The ability of H₂S to regulate vascular tone, inflammation, oxidative stress, and apoptosis might be particularly useful in the therapeutic management of critical illness. However, neither the inhalation of gaseous H₂S, nor the administration of inorganic H₂S-releasing salts or slow-releasing H₂S-donors are feasible for clinical use. Na₂S₂O₃ is a clinically approved compound with a good safety profile and is able to release H₂S, in particular under hypoxic conditions. Pre-clinical studies show promise for Na₂S₂O₃ in the acute management of critical illness. A current clinical trial is investigating the therapeutic potential for Na₂S₂O₃ in myocardial infarct. Pre-eclampsia and COVID-19 pneumonia might be relevant targets for future clinical trials.

Effects of Sodium Thiosulfate During Resuscitation From Trauma-and-Hemorrhage in Cystathionine Gamma Lyase (CSE) Knockout Mice

BACKGROUND

Sodium thiosulfate (Na2S2O3) is a clinically established drug with antioxidant and sulphide-releasing properties. Na2S2O3 mediated neuro- and cardioprotective effects in ischemia/reperfusion models and anti-inflammatory effects in LPS-induced acute lung injury. Moreover, Na2S2O3 improved lung function during resuscitation from hemorrhagic shock in swine with pre-existing atherosclerosis, characterized by decreased expression of cystathionine γ-lyase (CSE), a major source of hydrogen sulfide (H2S) synthesis in the vasculature. Based on these findings, we investigated the effects of Na2S2O3 administration during resuscitation from trauma-and-hemorrhage in mice under conditions of whole body CSE deficit.

METHODS

After blast wave-induced blunt chest trauma and surgical instrumentation, CSE knockout (CSE-/-) mice underwent 1 h of hemorrhagic shock (MAP 35 ± 5 mm Hg). At the beginning of resuscitation comprising retransfusion, norepinephrine support and lung-protective mechanical ventilation, animals received either i.v. Na2S2O3 (0.45 mg g-1, n = 12) or vehicle (saline, n = 13). Hemodynamics, acid-base status, metabolism using stable isotopes, and visceral organ function were assessed. Blood and organs were collected for analysis of cytokines, mitochondrial respiratory capacity, and immunoblotting.

RESULTS

Na2S2O3 treatment improved arterial paO2 (P = 0.03) coinciding with higher lung tissue glucocorticoid receptor expression. Norepinephrine requirements were lower in the Na2S2O3 group (P < 0.05), which was associated with lower endogenous glucose production and higher urine output. Na2S2O3 significantly increased renal tissue IκBα and heme oxygenase-1 expression, whereas it lowered kidney IL-6 and MCP-1 levels.

CONCLUSION

Na2S2O3 exerted beneficial effects during resuscitation of murine trauma-and-hemorrhage in CSE-/- mice, confirming and extending the previously described organ-protective and anti-inflammatory properties of Na2S2O3. The findings make Na2S2O3 a potentially promising therapeutic option in the context of impaired CSE activity and/or reduced endogenous H2S availability.

Oxytocin and Related Peptide Hormones: Candidate Anti-Inflammatory Therapy in Early Stages of Sepsis

Sepsis is a potentially life-threatening systemic inflammatory syndrome characterized by dysregulated host immunological responses to infection. Uncontrolled immune cell activation and exponential elevation in circulating cytokines can lead to sepsis, septic shock, multiple organ dysfunction syndrome, and death. Sepsis is associated with high re-hospitalization and recovery may be incomplete, with long term sequelae including post-sepsis syndrome. Consequently, sepsis continues to be a leading cause of morbidity and mortality across the world. In our recent review of human chorionic gonadotropin (hCG), we noted that its major properties including promotion of fertility, parturition, and lactation were described over a century ago. By contrast, the anti-inflammatory properties of this hormone have been recognized only more recently. Vasopressin, a hormone best known for its anti-diuretic effect, also has anti-inflammatory actions. Surprisingly, vasopressin's close cousin, oxytocin, has broader and more potent anti-inflammatory effects than vasopressin and a larger number of pre-clinical studies supporting its potential role in limiting sepsis-associated organ damage. This review explores possible links between oxytocin and related octapeptide hormones and sepsis-related modulation of pro-inflammatory and anti-inflammatory activities.

Localization of the hydrogen sulfide and oxytocin systems at the depth of the sulci in a porcine model of acute subdural hematoma

In the porcine model discussed in this review, the acute subdural hematoma was induced by subdural injection of autologous blood over the left parietal cortex, which led to a transient elevation of the intracerebral pressure, measured by bilateral neuromonitoring. The hematoma-induced brain injury was associated with albumin extravasation, oxidative stress, reactive astrogliosis and microglial activation in the ipsilateral hemisphere. Further proteins and injury markers were validated to be used for immunohistochemistry of porcine brain tissue. The cerebral expression patterns of oxytocin, oxytocin receptor, cystathionine-γ-lyase and cystathionine-β-synthase were particularly interesting: these four proteins all co-localized at the base of the sulci, where pressure-induced brain injury elicits maximum stress. In this context, the pig is a very relevant translational model in contrast to the rodent brain. The structure of the porcine brain is very similar to the human: the presence of gyri and sulci (gyrencephalic brain), white matter to grey matter proportion and tentorium cerebelli. Thus, pressure-induced injury in the porcine brain, unlike in the rodent brain, is reflective of the human pathophysiology.

The Gasotransmitter Hydrogen Sulfide and the Neuropeptide Oxytocin as Potential Mediators of Beneficial Cardiovascular Effects through Meditation after Traumatic Events

Trauma and its related psychological and somatic consequences are associated with higher cardiovascular morbidity. The regulation of both the gasotransmitter hydrogen sulfide (H2S) and the neuropeptide oxytocin (OT) have been reported to be affected during physical and psychological trauma. Both mediators are likely molecular correlates of trauma-induced cardiovascular complications, because they share parallel roles and signaling pathways in the cardiovascular system, both locally as well as on the level of central regulation and the vagus nerve. Meditation can alter the structure of specific brain regions and can have beneficial effects on cardiovascular health. This perspective article summarizes the evidence pointing toward the significance of H2S and OT signaling in meditation-mediated cardio-protection.

H2S and Oxytocin Systems in Early Life Stress and Cardiovascular Disease

Today it is well established that early life stress leads to cardiovascular programming that manifests in cardiovascular disease, but the mechanisms by which this occurs, are not fully understood. This perspective review examines the relevant literature that implicates the dysregulation of the gasomediator hydrogen sulfide and the neuroendocrine oxytocin systems in heart disease and their putative mechanistic role in the early life stress developmental origins of cardiovascular disease. Furthermore, interesting hints towards the mutual interaction of the hydrogen sulfide and OT systems are identified, especially with regards to the connection between the central nervous and the cardiovascular system, which support the role of the vagus nerve as a communication link between the brain and the heart in stress-mediated cardiovascular disease.

Hydrogen Sulfide and the Immune System

Hydrogen sulfide (H₂S) is the "third gasotransmitter" recognized alongside nitric oxide (NO) and carbon monoxide (CO). H₂S exhibits an array of biological effects in mammalian cells as revealed by studies showing important roles in the cardiovascular system, in cell signalling processes, post-translational modifications and in the immune system. Regarding the latter, using pharmacological and genetic approaches scientists have shown this molecule to have both pro- and anti-inflammatory effects in mammalian systems. The anti-inflammatory effects of H₂S appeared to be due to its inhibitory action on the nuclear factor kappa beta signalling pathway; NF-kB representing a transcription factor involved in the regulation pro-inflammatory mediators like nitric oxide, prostaglandins, and cytokines. In contrast, results from several animal model describe a more complicated picture and report on pro-inflammatory effects linked to exposure to this molecule; linked to dosage used and point of administration of this molecule. Overall, roles for H₂S in several inflammatory diseases spanning arthritis, atherosclerosis, sepsis, and asthma have been described by researchers. In light this work fascinating research, this chapter will cover H₂S biology and its many roles in the immune system.

Porcine models of acute kidney injury

Pigs represent a potentially attractive model for medical research. Similar body size and physiological patterns of kidney injury that more closely mimic those described in humans make larger animals attractive for experimentation. Using larger animals, including pigs, to investigate the pathogenesis of acute kidney injury (AKI) also serves as an experimental bridge, narrowing the gap between clinical disease and preclinical discoveries. This article compares the advantages and disadvantages of large versus small AKI animal models and provides a comprehensive overview of the development and application of porcine models of AKI induced by clinically relevant insults, including ischemia-reperfusion, sepsis, and nephrotoxin exposure. The primary focus of this review is to evaluate the use of pigs for AKI studies by current investigators, including areas where more information is needed.

ΔMST and the Regulation of Cardiac CSE and OTR Expression in Trauma and Hemorrhage

Genetic deletion of 3-mercaptopyruvate sulfurtransferase (MST) is known to result in hypertension and cardiac hypertrophy in older mice, and is associated with increased anxiety-like behaviors. Endogenous hydrogen sulfide (H2S) produced by MST in the mitochondria is also known to be involved in physiological and cellular bioenergetics, and its dysfunction associated with depressive behavior and increased cardiovascular morbidity. Interestingly, early life stress has been shown to lead to a significant loss of cystathionine-γ-lyase (CSE) and oxytocin receptor (OTR) expression in the heart. Thus, we were interested in testing the hypothesis of whether genetic MST mutation (ΔMST) would affect cardiac CSE and OTR expression and affect the mitochondrial respiration in a clinically relevant, resuscitated, mouse model of trauma and hemorrhagic shock. In ΔMST mice, we found a reduction of CSE and OTR in both the naive as well as injured state, in contrast to the wild type (wt) controls. Interestingly, the ΔMST showed a different complex IV response to injury than the wt controls, although our claims are based on the non-demonstrated assumption that naive wt and naive ΔMST mice have comparable complex IV activity. Finally, hemorrhagic shock led to a reduction of CSE and OTR, confirming previous results in the injured mouse heart. To date, the exact mechanisms of the cardiac interaction between H2S and OT are not clear, but they point the way to potential cardioprotective therapies.

The Interaction of the Endogenous Hydrogen Sulfide and Oxytocin Systems in Fluid Regulation and the Cardiovascular System

The purpose of this review is to explore the parallel roles and interaction of hydrogen sulfide (H2S) and oxytocin (OT) in cardiovascular regulation and fluid homeostasis. Their interaction has been recently reported to be relevant during physical and psychological trauma. However, literature reports on H2S in physical trauma and OT in psychological trauma are abundant, whereas available information regarding H2S in psychological trauma and OT in physical trauma is much more limited. This review summarizes recent direct and indirect evidence of the interaction of the two systems and their convergence in downstream nitric oxide-dependent signaling pathways during various types of trauma, in an effort to better understand biological correlates of psychosomatic interdependencies.

Cerebral Immunohistochemical Characterization of the H2S and the Oxytocin Systems in a Porcine Model of Acute Subdural Hematoma

The hydrogen sulfide (H₂S) and the oxytocin/oxytocin receptor (OT/OTR) systems interact in trauma and are implicated in vascular protection and regulation of fluid homeostasis. Acute brain injury is associated with pressure-induced edema formation, blood brain barrier disruption, and neuro-inflammation. The similarities in brain anatomy: size, gyrencephalic organization, skull structure, may render the pig a highly relevant model for translational medicine. Cerebral biomarkers for pigs for pathophysiological changes and neuro-inflammation are limited. The current study aims to characterize the localization of OT/OTR and the endogenous H₂S producing enzymes together with relevant neuro-inflammatory markers on available porcine brain tissue from an acute subdural hematoma (ASDH) model. In a recent pilot study, anesthetized pigs underwent ASDH by injection of 20 mL of autologous blood above the left parietal cortex and were resuscitated with neuro-intensive care measures. After 54 h of intensive care, the animals were sacrificed, the brain was removed and analyzed via immunohistochemistry. The endogenous H₂S producing enzymes cystathionine-ɤ-lyase (CSE) and cystathionine-β-synthase (CBS), the OTR, and OT were localized in neurons, vasculature and parenchyma at the base of sulci, where pressure-induced injury leads to maximal stress in the gyrencephalic brain. The pathophysiological changes in response to brain injury in humans and pigs, we show here, are comparable. We additionally identified modulators of brain injury to further characterize the pathophysiology of ASDH and which may indicate future therapeutic approaches.

The Role of Glucocorticoid Receptor and Oxytocin Receptor in the Septic Heart in a Clinically Relevant, Resuscitated Porcine Model With Underlying Atherosclerosis

The pathophysiology of sepsis-induced myocardial dysfunction is not resolved to date and comprises inflammation, barrier dysfunction and oxidative stress. Disease-associated reduction of tissue cystathionine-γ-lyase (CSE) expression, an endogenous H₂S-producing enzyme, is associated with oxidative stress, barrier dysfunction and organ injury. CSE-mediated cardio-protection has been suggested to be related the upregulation of oxytocin receptor (OTR). CSE can also mediate glucocorticoid receptor (GR) signaling, which is important for normal heart function. A sepsis-related loss of cardiac CSE expression associated with impaired organ function has been reported previously. The aim of this current post hoc study was to investigate the role of cardiac GR and OTR after polymicrobial sepsis in a clinically relevant, resuscitated, atherosclerotic porcine model. Anesthetized and instrumented FBM (Familial Hypercholesterolemia Bretoncelles Meishan) pigs with high fat diet-induced atherosclerosis underwent poly-microbial septic shock (n = 8) or sham procedure (n = 5), and subsequently received intensive care therapy with fluid and noradrenaline administration for 24 h. Cardiac protein expression and mRNA levels were analyzed. Systemic troponin, a marker of cardiac injury, was significantly increased in septic animals in contrast to sham, whereas OTR and GR expression in septic hearts were reduced, along with a down-regulation of anti-inflammatory GR target genes and the antioxidant transcription factor NRF2. These results suggest a potential interplay between GR, CSE, and OTR in sepsis-mediated oxidative stress, inflammation and cardiac dysfunction.

Cystathionine-γ-lyase expression is associated with mitochondrial respiration during sepsis-induced acute kidney injury in swine with atherosclerosis

Background

Sepsis is associated with disturbed glucose metabolism and reduced mitochondrial activity and biogenesis, ultimately leading to multiple organ dysfunction, e.g., acute kidney injury (AKI). Cystathionine-γ-lyase (CSE), the major cardiovascular source of endogenous H₂S release, is implicated in the regulation of glucose metabolism and mitochondrial activity through a PGC1α-dependent mechanism, and critical for kidney function. Atherosclerosis is associated with mitochondrial dysfunction and reduced CSE expression. Thus, the aim of this post hoc study was to test the hypothesis whether there is an interplay between CSE expression and kidney dysfunction, mitochondrial activity, and oxidative/nitrosative stress in porcine septic AKI with underlying coronary artery disease.

Methods

This study is a post hoc analysis of material from anesthetized and instrumented swine with a high fat diet-induced hypercholesterolemia and atherosclerosis undergoing faecal peritonitis-induced septic shock or sham procedure and intensive care (comprising fluid resuscitation and continuous i.v. noradrenaline (NoA) infusion) for 24 h. Glucose metabolism was quantified from blood ¹³C₆-glucose and expiratory ¹³CO₂/¹²CO₂ isotope enrichment during ¹³C₆-glucose infusion. Mitochondrial activity was determined by high-resolution respirometry. CSE and PGC1α expression, as well as nitrotyrosine formation and albumin extravasation, were quantified by immunohistochemistry of formalin-fixed kidney paraffin sections.

Results

Sepsis was associated with lactic acidosis (p = 0.004) and AKI (50% fall of creatinine clearance (CrCl), p = 0.019). While both whole-body glucose production (p = 0.004) and oxidation (p = 0.006) were increased, kidney tissue mitochondrial respiration was reduced (p = 0.028), coinciding with decreased CSE (p = 0.003) and PGC1α (p = 0.003) expression. Albumin extravasation (p = 0.011) and nitrotyrosine formation (p = 0.008) were increased in septic kidneys.

Conclusions

Sepsis-induced AKI is associated with disturbed mitochondrial respiration and biogenesis, which may be aggravated by oxidative and nitrosative stress. Our results confirm previous data in murine septic shock and porcine hemorrhage and resuscitation on the crucial role of CSE for barrier integrity and kidney function.

Electronic supplementary material

The online version of this article (10.1186/s40635-018-0208-z) contains supplementary material, which is available to authorized users.

Interaction of the hydrogen sulfide system with the oxytocin system in the injured mouse heart

Background

Both the hydrogen sulfide/cystathionine-γ-lyase (H₂S/CSE) and oxytocin/oxytocin receptor (OT/OTR) systems have been reported to be cardioprotective. H₂S can stimulate OT release, thereby affecting blood volume and pressure regulation. Systemic hyper-inflammation after blunt chest trauma is enhanced in cigarette smoke (CS)-exposed CSE^−/− mice compared to wildtype (WT). CS increases myometrial OTR expression, but to this point, no data are available on the effects CS exposure on the cardiac OT/OTR system. Since a contusion of the thorax (Txt) can cause myocardial injury, the aim of this post hoc study was to investigate the effects of CSE^−/− and exogenous administration of GYY4137 (a slow release H₂S releasing compound) on OTR expression in the heart, after acute on chronic disease, of CS exposed mice undergoing Txt.

Methods

This study is a post hoc analysis of material obtained in wild type (WT) homozygous CSE^−/− mice after 2-3 weeks of CS exposure and subsequent anesthesia, blast wave-induced TxT, and surgical instrumentation for mechanical ventilation (MV) and hemodynamic monitoring. CSE^−/− animals received a 50 μg/g GYY4137-bolus after TxT. After 4h of MV, animals were exsanguinated and organs were harvested. The heart was cut transversally, formalin-fixed, and paraffin-embedded. Immunohistochemistry for OTR, arginine-vasopressin-receptor (AVPR), and vascular endothelial growth factor (VEGF) was performed with naïve animals as native controls.

Results

CSE^−/− was associated with hypertension and lower blood glucose levels, partially and significantly restored by GYY4137 treatment, respectively. Myocardial OTR expression was reduced upon injury, and this was aggravated in CSE^−/−. Exogenous H₂S administration restored myocardial protein expression to WT levels.

Conclusions

This study suggests that cardiac CSE regulates cardiac OTR expression, and this effect might play a role in the regulation of cardiovascular function.

Preparation and characterization of universal Fe3O4@SiO2/CdTe nanocomposites for rapid and facile detection and separation of membrane proteins

The separation and enrichment of cell membrane proteins was achieved by the construction of bi-functional magnetic fluorescent nanoprobes.

Cooperative Oxygen Sensing by the Kidney and Carotid Body in Blood Pressure Control

Oxygen sensing mechanisms are vital for homeostasis and survival. When oxygen levels are too low (hypoxia), blood flow has to be increased, metabolism reduced, or a combination of both, to counteract tissue damage. These adjustments are regulated by local, humoral, or neural reflex mechanisms. The kidney and the carotid body are both directly sensitive to falls in the partial pressure of oxygen and trigger reflex adjustments and thus act as oxygen sensors. We hypothesize a cooperative oxygen sensing function by both the kidney and carotid body to ensure maintenance of whole body blood flow and tissue oxygen homeostasis. Under pathological conditions of severe or prolonged tissue hypoxia, these sensors may become continuously excessively activated and increase perfusion pressure chronically. Consequently, persistence of their activity could become a driver for the development of hypertension and cardiovascular disease. Hypoxia-mediated renal and carotid body afferent signaling triggers unrestrained activation of the renin angiotensin-aldosterone system (RAAS). Renal and carotid body mediated responses in arterial pressure appear to be synergistic as interruption of either afferent source has a summative effect of reducing blood pressure in renovascular hypertension. We discuss that this cooperative oxygen sensing system can activate/sensitize their own afferent transduction mechanisms via interactions between the RAAS, hypoxia inducible factor and erythropoiesis pathways. This joint mechanism supports our view point that the development of cardiovascular disease involves afferent nerve activation.

International Union of Basic and Clinical Pharmacology. CII: Pharmacological Modulation of H2S Levels: H2S Donors and H2S Biosynthesis Inhibitors

Over the last decade, hydrogen sulfide (H2S) has emerged as an important endogenous gasotransmitter in mammalian cells and tissues. Similar to the previously characterized gasotransmitters nitric oxide and carbon monoxide, H2S is produced by various enzymatic reactions and regulates a host of physiologic and pathophysiological processes in various cells and tissues. H2S levels are decreased in a number of conditions (e.g., diabetes mellitus, ischemia, and aging) and are increased in other states (e.g., inflammation, critical illness, and cancer). Over the last decades, multiple approaches have been identified for the therapeutic exploitation of H2S, either based on H2S donation or inhibition of H2S biosynthesis. H2S donation can be achieved through the inhalation of H2S gas and/or the parenteral or enteral administration of so-called fast-releasing H2S donors (salts of H2S such as NaHS and Na2S) or slow-releasing H2S donors (GYY4137 being the prototypical compound used in hundreds of studies in vitro and in vivo). Recent work also identifies various donors with regulated H2S release profiles, including oxidant-triggered donors, pH-dependent donors, esterase-activated donors, and organelle-targeted (e.g., mitochondrial) compounds. There are also approaches where existing, clinically approved drugs of various classes (e.g., nonsteroidal anti-inflammatories) are coupled with H2S-donating groups (the most advanced compound in clinical trials is ATB-346, an H2S-donating derivative of the non-steroidal anti-inflammatory compound naproxen). For pharmacological inhibition of H2S synthesis, there are now several small molecule compounds targeting each of the three H2S-producing enzymes cystathionine-β-synthase (CBS), cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase. Although many of these compounds have their limitations (potency, selectivity), these molecules, especially in combination with genetic approaches, can be instrumental for the delineation of the biologic processes involving endogenous H2S production. Moreover, some of these compounds (e.g., cell-permeable prodrugs of the CBS inhibitor aminooxyacetate, or benserazide, a potentially repurposable CBS inhibitor) may serve as starting points for future clinical translation. The present article overviews the currently known H2S donors and H2S biosynthesis inhibitors, delineates their mode of action, and offers examples for their biologic effects and potential therapeutic utility.

The Role of Hydrogen Sulfide on Cardiovascular Homeostasis: An Overview with Update on Immunomodulation

Hydrogen sulfide (H₂S), the third endogenous gaseous signaling molecule alongside nitric oxide (NO) and carbon monoxide, is synthesized by multiple enzymes in cardiovascular system. Similar to other gaseous mediators, H₂S has demonstrated a variety of biological activities, including anti-oxidative, anti-apoptotic, pro-angiogenic, vasodilating capacities and endothelial NO synthase modulating activity, and regulates a wide range of pathophysiological processes in cardiovascular disorders. However, the underlying mechanisms by which H₂S mediates cardiovascular homeostasis are not fully understood. This review focuses on the recent progress on functional and mechanistic aspects of H₂S in the inflammatory and immunoregulatory processes of cardiovascular disorders, importantly myocardial ischemia, heart failure, and atherosclerosis. Moreover, we highlight the challenges for developing H₂S-based therapy to modulate the pathological processes in cardiovascular diseases. A better understanding of the immunomodulatory and biochemical functions of H₂S might provide new therapeutic strategies for these cardiovascular diseases.