Effect of type 1 diabetes on the production and vasoactivity of hydrogen sulfide in rat middle cerebral arteries

Recent Advances in Molecular Research on Hydrogen Sulfide (H2S) Role in Diabetes Mellitus (DM)-A Systematic Review

Abundant experimental data suggest that hydrogen sulfide (H₂S) is related to the pathophysiology of Diabetes Mellitus (DM). Multiple molecular mechanisms, including receptors, membrane ion channels, signalingmolecules, enzymes, and transcription factors, are known to be responsible for the H₂S biological actions; however, H₂S is not fully documented as a gaseous signaling molecule interfering with DM and vascular-linked pathology. In recent decades, multiple approaches regarding therapeutic exploitation of H₂S have been identified, either based on H₂S exogenous apport or on its modulated endogenous biosynthesis. This paper aims to synthesize and systematize, as comprehensively as possible, the recent literature-related data regarding the therapeutic/rehabilitative role of H₂S in DM. This review was conducted following the “Preferred reporting items for systematic reviews and meta-analyses” (PRISMA) methodology, interrogating five international medically renowned databases by specific keyword combinations/“syntaxes” used contextually, over the last five years (2017–2021). The respective search/filtered and selection methodology we applied has identified, in the first step, 212 articles. After deploying the next specific quest steps, 51 unique published papers qualified for minute analysis resulted. To these bibliographic resources obtained through the PRISMA methodology, in order to have the best available information coverage, we added 86 papers that were freely found by a direct internet search. Finally, we selected for a connected meta-analysis eight relevant reports that included 1237 human subjects elicited from clinical trial registration platforms. Numerous H₂S releasing/stimulating compounds have been produced, some being used in experimental models. However, very few of them were further advanced in clinical studies, indicating that the development of H₂S as a therapeutic agent is still at the beginning.

Current Perspective of Hydrogen Sulfide as a Novel Gaseous Modulator of Oxidative Stress in Glaucoma

Glaucoma is a group of diseases characterized by the progressive loss of retinal ganglion cells and their axons. Elevated intraocular pressure (IOP) is the main clinical manifestation of glaucoma. Despite being in the focus of the studies for decades, the characteristic and the exact pathology of neurodegeneration in glaucoma remains unclear. Oxidative stress is believed to be one of the main risk factors in neurodegeneration, especially its damage to the retinal ganglion cells. Hydrogen sulfide (H₂S), the recently recognized gas signaling molecule, plays a pivotal role in the nervous system, vascular system, and immune system. It has also shown properties in regulating oxidative stress through different pathways in vivo. In this review, we summarize the distribution and the properties of H₂S within the eye with an emphasis on its role in modulating oxidative stress in glaucoma.

The Potential Role of Hydrogen Sulfide in the Regulation of Cerebrovascular Tone

A better understanding of the regulation of cerebrovascular circulation is of great importance because stroke and other cerebrovascular diseases represent a major concern in healthcare leading to millions of deaths yearly. The circulation of the central nervous system is regulated in a highly complex manner involving many local factors and hydrogen sulfide (H₂S) is emerging as one such possible factor. Several lines of evidence support that H₂S takes part in the regulation of vascular tone. Examinations using either exogenous treatment with H₂S donor molecules or alterations to the enzymes that are endogenously producing this molecule revealed numerous important findings about its physiological and pathophysiological role. The great majority of these studies were performed on vessel segments derived from the systemic circulation but there are important observations made using cerebral vessels as well. The findings of these experimental works indicate that H₂S is having a complex, pleiotropic effect on the vascular wall not only in the systemic circulation but in the cerebrovascular region as well. In this review, we summarize the most important experimental findings related to the potential role of H₂S in the cerebral circulation.

Role of Endothelial Dysfunction in Cardiovascular Diseases: The Link Between Inflammation and Hydrogen Sulfide

Endothelial cells are important constituents of blood vessels that play critical roles in cardiovascular homeostasis by regulating blood fluidity and fibrinolysis, vascular tone, angiogenesis, monocyte/leukocyte adhesion, and platelet aggregation. The normal vascular endothelium is taken as a gatekeeper of cardiovascular health, whereas abnormality of vascular endothelium is a major contributor to a plethora of cardiovascular ailments, such as atherosclerosis, aging, hypertension, obesity, and diabetes. Endothelial dysfunction is characterized by imbalanced vasodilation and vasoconstriction, elevated reactive oxygen species (ROS), and proinflammatory factors, as well as deficiency of nitric oxide (NO) bioavailability. The occurrence of endothelial dysfunction disrupts the endothelial barrier permeability that is a part of inflammatory response in the development of cardiovascular diseases. As such, abrogation of endothelial cell activation/inflammation is of clinical relevance. Recently, hydrogen sulfide (H₂S), an entry as a gasotransmitter, exerts diverse biological effects through acting on various targeted signaling pathways. Within the cardiovascular system, the formation of H₂S is detected in smooth muscle cells, vascular endothelial cells, and cardiomyocytes. Disrupted H₂S bioavailability is postulated to be a new indicator for endothelial cell inflammation and its associated endothelial dysfunction. In this review, we will summarize recent advances about the roles of H₂S in endothelial cell homeostasis, especially under pathological conditions, and discuss its putative therapeutic applications in endothelial inflammation-associated cardiovascular disorders.

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.

Vascular biology of hydrogen sulfide

Hydrogen sulfide (H₂S) is a ubiquitous signaling molecule with important functions in many mammalian organs and systems. Observations in the 1990s ascribed physiological actions to H₂S in the nervous system, proposing that this gasotransmitter acts as a neuromodulator. Soon after that, the vasodilating properties of H₂S were demonstrated. In the past decade, H₂S was shown to exert a multitude of physiological effects in the vessel wall. H₂S is produced by vascular cells and exhibits antioxidant, antiapoptotic, anti-inflammatory, and vasoactive properties. In this concise review, we have focused on the impact of H₂S on vascular structure and function with an emphasis on angiogenesis, vascular tone, vascular permeability and atherosclerosis. H₂S reduces arterial blood pressure, limits atheromatous plaque formation, and promotes vascularization of ischemic tissues. Although the beneficial properties of H₂S are well established, mechanistic insights into the molecular pathways implicated in disease prevention and treatment remain largely unexplored. Unraveling the targets and downstream effectors of H₂S in the vessel wall in the context of disease will aid in translation of preclinical observations. In addition, acute regulation of H₂S production is still poorly understood and additional work delineating the pathways regulating the enzymes that produce H₂S will allow pharmacological manipulation of this pathway. As the field continues to grow, we expect that H₂S-related compounds will find their way into clinical trials for diseases affecting the blood vessels.

Gasotransmitters in Vascular Complications of Diabetes

In the past decades three gaseous signaling molecules-so-called gasotransmitters-have been identified: nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S). These gasotransmitters are endogenously produced by different enzymes in various cell types and play an important role in physiology and disease. Despite their specific functions, all gasotransmitters share the capacity to reduce oxidative stress, induce angiogenesis, and promote vasorelaxation. In patients with diabetes, a lower bioavailability of the different gasotransmitters is observed when compared with healthy individuals. As yet, it is unknown whether this reduction precedes or results from diabetes. The increased risk for vascular disease in patients with diabetes, in combination with the extensive clinical, financial, and societal burden, calls for action to either prevent or improve the treatment of vascular complications. In this Perspective, we present a concise overview of the current data on the bioavailability of gasotransmitters in diabetes and their potential role in the development and progression of diabetes-associated microvascular (retinopathy, neuropathy, and nephropathy) and macrovascular (cerebrovascular, coronary artery, and peripheral arterial diseases) complications. Gasotransmitters appear to have both inhibitory and stimulatory effects in the course of vascular disease development. This Perspective concludes with a discussion on gasotransmitter-based interventions as a therapeutic option.

The role of H2S bioavailability in endothelial dysfunction

Endothelial dysfunction (EDF) reflects pathophysiological changes in the phenotype and functions of endothelial cells that result from and/or contribute to a plethora of cardiovascular diseases. We review the role of hydrogen sulfide (H2S) in the pathogenesis of EDF, one of the fastest advancing research topics. Conventionally treated as an environment pollutant, H2S is also produced in endothelial cells and participates in the fine regulation of endothelial integrity and functions. Disturbed H2S bioavailability has been suggested to be a novel indicator of EDF progress and prognosis. EDF manifests in different forms in multiple pathologies, but therapeutics aimed at remedying altered H2S bioavailability may benefit all.

Tracheal suctioning improves gas exchange but not hemodynamics in asphyxiated lambs with meconium aspiration

BACKGROUND

Current neonatal resuscitation guidelines recommend tracheal suctioning of nonvigorous neonates born through meconium-stained amniotic fluid.

METHODS

We evaluated the effect of tracheal suctioning at birth in 29 lambs with asphyxia induced by cord occlusion and meconium aspiration during gasping.

RESULTS

Tracheal suctioning at birth (n = 15) decreased amount of meconium in distal airways (53 ± 29 particles/mm(2) lung area) compared to no suction (499 ± 109 particles/mm(2); n = 14; P < 0.001). Three lambs in the suction group had cardiac arrest during suctioning, requiring chest compressions and epinephrine. Onset of ventilation was delayed in the suction group (146 ± 11 vs. 47 ± 3 s in no-suction group; P = 0.005). There was no difference in pulmonary blood flow, carotid blood flow, and pulmonary or systemic blood pressure between the two groups. Left atrial pressure was significantly higher in the suction group. Tracheal suctioning resulted in higher Pao2/FiO2 levels (122 ± 21 vs. 78 ± 10 mm Hg) and ventilator efficiency index (0.3 ± 0.05 vs.0.16 ± 0.03). Two lambs in the no-suction group required inhaled nitric oxide. Lung 3-nitrotyrosine levels were higher in the suction group (0.65 ± 0.03 ng/µg protein) compared with the no-suction group (0.47 ± 0.06).

CONCLUSION

Tracheal suctioning improves oxygenation and ventilation. Suctioning does not improve pulmonary/systemic hemodynamics or oxidative stress in an ovine model of acute meconium aspiration with asphyxia.

Modulation of hydrogen sulfide by vascular hypoxia

Hydrogen sulfide (H₂S) has emerged as a key regulator of cardiovascular function. This gasotransmitter is produced in the vasculature and is involved in numerous processes that promote vascular homeostasis, including vasodilation and endothelial cell proliferation. Although H₂S plays a role under physiological conditions, it has become clear in recent years that hypoxia modulates the production and action of H₂S. Furthermore, there is growing evidence that H₂S is cytoprotective in the face of hypoxic insults. This review focuses on the synthesis and signaling of H₂S in hypoxic conditions in the vasculature, and highlights recent studies providing evidence that H₂S is a potential therapy for preventing tissue damage in hypoxic conditions.

Hydrogen sulfide treatment reduces blood pressure and oxidative stress in angiotensin II-induced hypertensive mice

Hydrogen sulfide (H2S) is increasingly recognized as a gasotransmitter with protective effects in the cardiovascular system. The aim of the study was to examine the effects of chronic NaHS treatment on blood pressure, vascular function and oxidative stress in an in vivo model of hypertension and oxidative stress. Male C57Bl6/J mice were rendered hypertensive with 0.7 mg kg(-1) per day angiotensin II (AngII) for 14 days administered via implanted mini-pumps. The mice were treated with NaHS (10 μmol kg(-1) per day) to deliver H2S or an inhibitor of cystathionine-γ-lyase, DL-propargylglycine (PPG 30 mg kg(-1) per day) via intraperitoneal (i.p.) injection. Systolic blood pressure was measured and vascular function examined by myography. Vascular superoxide production was measured by lucigenin-enhanced chemiluminescence. AngII infusion significantly increased systolic blood pressure (P < 0.001). This increase was significantly attenuated by treatment with NaHS (P < 0.001). Both aortic endothelial function and NO bioavailability were significantly attenuated in the AngII group (P < 0.01) but this attenuation was reversed by NaHS treatment. Similarly, aortic superoxide anion production was significantly enhanced by AngII (P < 0.01), and this was reversed by NaHS treatment, and also exacerbated by PPG treatment (P < 0.001). These data show that in a mouse model of hypertension and oxidative stress induced by AngII, exogenous H2S treatment in vivo reduces blood pressure, endothelial dysfunction and vascular oxidative stress, while inhibiting endogenous H2S production in vivo is deleterious. This furthers the evidence that H2S is a vasoprotective molecule that may be a useful treatment target in cardiovascular disease.