Transdermal Delivery of a Hydrogen Sulphide Donor, ADT-OH Using Aqueous Gel Formulations for the Treatment of Impaired Vascular Function: an Ex Vivo Study.

PURPOSE: Hydrogen sulphide (H2S) is an important signalling molecule involved in the regulation of several physiological and pathophysiological processes. The objective of this study was to investigate the feasibility of transdermal delivery of ADT-OH, a H2S donor, by investigating the transdermal flux of aqueous gels loaded with penetration enhancers or liposomes. Furthermore, we explored the ability of permeated ADT-OH to promote angiogenesis and mitochondrial bioenergetics in HUVEC cells. METHODS: Aqueous hypromellose gels (5% w/v) were prepared with up to 10% v/v propylene glycol (PG) or deformable liposomes with 0.025% w/w ADT-OH. ADT-OH permeation from formulations across excised murine skin into PBS was quantified over 24 h using HPLC-UV detection. Media was collected and applied to HUVEC cells to evidence ADT-OH functionality following permeation. Tube formation assays were performed as indicative of angiogenesis and mitochondrial oxygen consumption was evaluated using a Seahorse XF24. RESULTS: Increasing the loading of PG caused an increase in ADT-OH permeation rate across skin and a decrease in dermal drug retention whereas liposomal gels produced a slow-release profile. Treatment of HUVEC's using conditioned media collected from the ADT-OH loaded permeation studies enhanced tube formation and the basal oxygen consumption rates after 30 min of treatment. CONCLUSIONS: These findings demonstrate that transdermal delivery of ADT-OH may provide a promising approach in the treatment of impaired vascular function. Gels prepared with 10% v/v PG have the potential for use in conditions requiring rapid H2S release whereas liposomal loaded gels for treatment requiring sustained H2S release.

H2S Donors and Their Use in Medicinal Chemistry.

Hydrogen sulfide (H2S) is a ubiquitous gaseous signaling molecule that has an important role in many physiological and pathological processes in mammalian tissues, with the same importance as two others endogenous gasotransmitters such as NO (nitric oxide) and CO (carbon monoxide). Endogenous H2S is involved in a broad gamut of processes in mammalian tissues including inflammation, vascular tone, hypertension, gastric mucosal integrity, neuromodulation, and defense mechanisms against viral infections as well as SARS-CoV-2 infection. These results suggest that the modulation of H2S levels has a potential therapeutic value. Consequently, synthetic H2S-releasing agents represent not only important research tools, but also potent therapeutic agents. This review has been designed in order to summarize the currently available H2S donors; furthermore, herein we discuss their preparation, the H2S-releasing mechanisms, and their -biological applications.

Hydrogen Sulfide Ameliorates Lipopolysaccharide-Induced Memory Impairment in Mice by Reducing Apoptosis, Oxidative, and Inflammatory Effects.

Hydrogen sulfide (H2S) is reported to have a neuroprotective activity; however, the role of H2S in neuroinflammation-induced neuronal damage is ambiguous. Here, we aimed to evaluate the underlying mechanisms for the neuroprotective effect of NaHS, a known H2S donor, against lipopolysaccharide (LPS)-induced memory impairment (MI). All the treatments were administered for 28 days, and LPS (0.25 mg/kg i.p.) was co-administered intermittently for 7 days from days 15 to 21. Morris water maze (MWM) and Y-maze tests were performed to evaluate MI. Neurodegeneration was histopathologically examined, and the brain homogenates were characterized for reduced glutathione (GSH), superoxide dismutase (SOD), malondialdehyde (MDA), tumor necrosis factor (TNF)-α, interleukin (IL)-6, caspase-3, c-Jun, and acetylcholinesterase (AChE) by biochemical analysis. H2S administration significantly improved spatial and working memory in MWM and Y-maze tasks, respectively. Exogenous H2S significantly reversed LPS-induced oxidative stress as evidenced by improved GSH, MDA, and SOD levels. H2S pretreatment significantly attenuated LPS-induced apoptosis and inflammation by decreasing c-Jun and caspase-3 levels and inhibiting TNF-α and IL-6, respectively. The decrease in these markers was supported by H&E and Nissl staining, which confirmed the anti-necrotic activity of H2S. However, there was no significant improvement in LPS-induced increase in AChE activity. These results indicate that chronic systemic inflammation leads to neurodegeneration and MI and H2S exerts its neuroprotective effect due to its anti-oxidative, anti-inflammatory, and anti-apoptotic potential via modulation of JNK and extrinsic apoptosis pathways.

Subnormothermic Perfusion with H2S Donor AP39 Improves DCD Porcine Renal Graft Outcomes in an Ex Vivo Model of Kidney Preservation and Reperfusion.

Cold preservation is the standard of care for renal grafts. However, research on alternatives like perfusion at higher temperatures and supplementing preservation solutions with hydrogen sulfide (H2S) has gained momentum. In this study, we investigated whether adding H2S donor AP39 to porcine blood during subnormothermic perfusion at 21 °C improves renal graft outcomes. Porcine kidneys were nephrectomized after 30 min of clamping the renal pedicles and treated to 4 h of static cold storage (SCS) on ice or ex vivo subnormothermic perfusion at 21 °C with autologous blood alone (SNT) or with AP39 (SNTAP). All kidneys were reperfused ex vivo with autologous blood at 37 °C for 4 h. Urine output, histopathology and RNAseq were used to evaluate the renal graft function, injury and gene expression profiles, respectively. The SNTAP group exhibited significantly higher urine output than other groups during preservation and reperfusion, along with significantly lower apoptotic injury compared to the SCS group. The SNTAP group also exhibited differential pro-survival gene expression patterns compared to the SCS (downregulation of pro-apoptotic genes) and SNT (downregulation of hypoxia response genes) groups. Subnormothermic perfusion at 21 °C with H2S-supplemented blood improves renal graft outcomes. Further research is needed to facilitate the clinical translation of this approach.

The Potential of Hydrogen Sulfide Donors in Treating Cardiovascular Diseases.

Hydrogen sulfide (H2S) has long been considered as a toxic gas, but as research progressed, the idea has been updated and it has now been shown to have potent protective effects at reasonable concentrations. H2S is an endogenous gas signaling molecule in mammals and is produced by specific enzymes in different cell types. An increasing number of studies indicate that H2S plays an important role in cardiovascular homeostasis, and in most cases, H2S has been reported to be downregulated in cardiovascular diseases (CVDs). Similarly, in preclinical studies, H2S has been shown to prevent CVDs and improve heart function after heart failure. Recently, many H2S donors have been synthesized and tested in cellular and animal models. Moreover, numerous molecular mechanisms have been proposed to demonstrate the effects of these donors. In this review, we will provide an update on the role of H2S in cardiovascular activities and its involvement in pathological states, with a special focus on the roles of exogenous H2S in cardiac protection.

Metal-organic frameworks for therapeutic gas delivery.

Nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S) are gaseous signaling molecules (gasotransmitters) that regulate both physiological and pathological processes and offer therapeutic potential for the treatment of many diseases, such as cancer, cardiovascular disease, renal disease, bacterial and viral infections. However, the inherent labile nature of therapeutic gases results in difficulties in direct gases administration and their controlled delivery at clinically relevant ranges. Metal-organic frameworks (MOFs) with highly porous, stable, and easy-to-tailor properties have shown promising therapeutic gas delivery potential. Herein, we highlight the recent advances of MOF-based platforms for therapeutic gas delivery, either by endogenous (i.e., direct transfer of gases to targets) or exogenous (i.e., stimulating triggered release of gases) means. Reports that involve in vitro and/or in vivo studies are highlighted due to their high potential for clinical translation. Current challenges for clinical requirements and possible future innovative designs to meet variable healthcare needs are discussed.

Mechanisms underlying the vasorelaxant effect of hydrogen sulfide on human saphenous vein.

Hydrogen sulfide (H2 S) represents the third and the youngest member of the gaseous transmitters family. The dominant effect of H2 S on isolated vessels is vasodilation. As the mechanism of H2 S-induced relaxation in human vessels remains unclear, the present study aimed to investigate the effects of H2 S donor, sodium hydrosulfide (NaHS), on isolated human saphenous vein (HSV) and to determine the mechanism of action. Our results showed that NaHS (1 µM-3 mM) induced a concentration-dependent relaxation of endothelium-intact HSV rings pre-contracted by phenylephrine. Pre-treatment with L-NAME, ODQ and KT5823 significantly inhibited NaHS-induced relaxation, while indomethacin induced partial inhibition. Among K+ channel blockers, the combination of apamin and TRAM-34 significantly affected the relaxation produced by NaHS, while iberiotoxin and glibenclamide only reduced maximal relaxation of HSV. NaHS partially relaxed endothelium-intact rings pre-contracted by high K+ , as well as phenylephrine-contracted rings in the presence of nifedipine. Additionally, the incubation of HSV rings with NaHS increased NO production. These results demonstrate that NaHS produces the concentration- and endothelium-dependent relaxation of isolated HSV. Vasorelaxation to NaHS probably involves activation of NO/cGMP/PKG pathway and partially prostacyclin. In addition, different K+ channels subtypes, especially SKCa and IKCa , as well as BKCa and KATP channels in high concentrations of NaHS, probably participate in the NaHS-induced vasorelaxation.

Activation of Endogenous H2S Biosynthesis or Supplementation with Exogenous H2S Enhances Adipose Tissue Adipogenesis and Preserves Adipocyte Physiology in Humans.

Aims: To investigate the impact of exogenous hydrogen sulfide (H2S) and its endogenous biosynthesis on human adipocytes and adipose tissue in the context of obesity and insulin resistance. Results: Experiments in human adipose tissue explants and in isolated preadipocytes demonstrated that exogenous H2S or the activation of endogenous H2S biosynthesis resulted in increased adipogenesis, insulin action, sirtuin deacetylase, and PPARγ transcriptional activity, whereas chemical inhibition and gene knockdown of each enzyme generating H2S (CTH, CBS, MPST) led to altered adipocyte differentiation, cellular senescence, and increased inflammation. In agreement with these experimental data, visceral and subcutaneous adipose tissue expression of H2S-synthesising enzymes was significantly reduced in morbidly obese subjects in association with attenuated adipogenesis and increased markers of adipose tissue inflammation and senescence. Interestingly, weight-loss interventions (including bariatric surgery or diet/exercise) improved the expression of H2S biosynthesis-related genes. In human preadipocytes, the expression of CTH, CBS, and MPST genes and H2S production were dramatically increased during adipocyte differentiation. More importantly, the adipocyte proteome exhibiting persulfidation was characterized, disclosing that different proteins involved in fatty acid and lipid metabolism, the citrate cycle, insulin signaling, several adipokines, and PPAR, experienced the most dramatic persulfidation (85-98%). Innovation: No previous studies investigated the impact of H2S on human adipose tissue. This study suggests that the potentiation of adipose tissue H2S biosynthesis is a possible therapeutic approach to improve adipose tissue dysfunction in patients with obesity and insulin resistance. Conclusion: Altogether, these data supported the relevance of H2S biosynthesis in the modulation of human adipocyte physiology. Antioxid. Redox Signal. 35, 319-340.

Novel controlled and targeted releasing hydrogen sulfide system exerts combinational cerebral and myocardial protection after cardiac arrest.

BACKGROUND: Cardiac arrest (CA) is a leading cause of death worldwide. Even after successful cardiopulmonary resuscitation (CPR), the majorities of survivals are companied with permanent myocardial and cerebral injury. Hydrogen sulfide (H2S) has been recognized as a novel gasotransmitter exerting multiple organ protection; however, the lacks of ideal H2S donors which can controlled release H2S to targeted organs such as heart and brain limits its application. RESULTS: This work utilized mesoporous iron oxide nanoparticle (MION) as the carriers of diallyl trisulfide (DATS), with polyethylene glycol (PEG) and lactoferrin (LF) modified to MIONs to acquire the prolonged circulation time and brain-targeting effects, and a novel targeted H2S releasing system was constructed (DATS@MION-PEG-LF), which exhibited excellent biocompatibility, controlled-releasing H2S pattern, heart and brain targeting features, and the ability to be non-invasive traced by magnetic resonance imaging. DATS@MION-PEG-LF presented potent protective effects against cerebral and cardiac ischemic injury after CA in both in vitro hypoxia/reoxygenation models and in vivo CA/CPR models, which mainly involves anti-apoptosis, anti-inflammatory and anti-oxidant mechanisms. Accordingly, the cardiac and cerebral functions were obviously improved after CA/CPR, with potentially improved survival. CONCLUSIONS: The present work provides a unique platform for targeted controlled release of H2S based on MIONs, and offers a new method for combinational myocardial and cerebral protection from ischemic injury, bringing considerable benefits for CA patients.

In vitro anticancer activity of hydrogen sulfide and nitric oxide alongside nickel nanoparticle and novel mutations in their genes in CRC patients.

This study was carried out to assess the impact of nickel nanoparticles (NiNPs) as well as scorpion venom on colorectal cancer (CRC) cells in the presence and/or absence of 5-fluorouracil (5-FU), hydrogen sulfide (H2S), and nitric oxide (NO) donors and to determine alterations in endothelial NO synthase (eNOS) and cystathionine γ-lyase (CSE) enzyme-producing genes in CRC patients. The IC50 of both H2S and NO donors, along with NiNPs, were determined. The CRC cells were treated for 24hrs, and the cytotoxic activities were assessed using the MTT test. Moreover, the apoptosis was determined after 24hrs and 48hrs using TUNEL assay. Furthermore, the mutations in the eNOS gene (intron 4, -786T>C and 894 G>T) and CSE gene (1364GT) were determined using direct sequencing. The IC50 values for sodium disulfide (Na2S) and sodium nitroprusside (SNP) at 24hrs treatment were found to be 5 mM and 10-6 M, respectively, while the IC50 value for 5-FU was reached after 5-days of treatment in CRC cell line. Both black and yellow scorpion venoms showed no inhibition of cell proliferation after 24hrs treatment. Furthermore, Na2S showed a significant decrease in cell proliferation and an increase in apoptosis. Moreover, a co-treatment of SNP and 5-FU resulted in inhibition of the cytotoxic effect of 5-FU, while a combination treatment of NiNPs with Na2S, SNP, and 5-FU caused highly significant cytotoxicity. Direct sequencing reveals new mutations, mainly intronic variation in eNOS gene that has not previously been described in the database. These findings indicate that H2S promotes the anticancer efficiency of 5-FU in the presence of NiNPs while NO has antiapoptotic activity in CRC cell lines.

Portal Venous Flow Is Increased by Jejunal but Not Colonic Hydrogen Sulfide in a Nitric Oxide-Dependent Fashion in Rats.

Hydrogen sulfide (H2S) is a recently discerned endogenous signaling molecule that modulates the vascular system. Endogenous hydrogen sulfide has been shown to dilate both the mesenteric and portal vasculature. Gut microbiome, via sulfur reducing bacteria, is another source of H2S production within the gut lumen; this source of H2S is primarily produced and detoxified in the colon under physiologic conditions. Nitric oxide (NO), a major endogenous vasodilator in the portal circulation, participates in H2S-induced vasodilation in some vascular beds. We hypothesize that jejunal but not colonic H2S increases portal vein flow in a NO-dependent fashion. To evaluate the effects of luminal H2S, venous blood flow, portal venous pressure, and systemic venous pressure were measured in rats after administration of either vehicle or an H2S donor (NaHS) into the jejunum or the colon. We found that portal venous pressure and systemic pressure did not change and were similar between the three study groups. However, portal venous blood flow significantly increased following jejunal administration of NaHS but not in response to colonic NaHS or vehicle administration. To test the contribution of NO production to this response, another group of animals was treated with either an NO synthase inhibitor (N-Ω-nitro-L-arginine, L-NNA) or saline prior to jejunal NaHS infusion. After L-NNA pretreatment, NaHS caused a significant fall rather than increase in portal venous flow compared to saline pretreatment. These data demonstrate that H2S within the small intestine significantly increases portal venous blood flow in a NO-dependent fashion.

Hydrogen sulfide is a regulator of mammary gland development in prepubescent female mice.

The present study aimed to investigate the effects of exogenous H2S on mammary gland development in pubescent mice and to explore the underlying mechanism. The mouse mammary epithelial cell line HC11, along with C57BL/6J mice, were treated with different concentrations of sodium hydrosulfide (NaHS), which is a donor of H2S. The HC11 cell viability, pubescent mammary gland development, and the involvement of proliferative proteins and pathways were assessed by CCK­8 assay, EdU assay, whole mount staining, H&E staining, western blotting and reverse transcription­quantitative PCR. Both in vitro and in vivo, a low concentration of NaHS (100 µM in vitro; 9 mg/kg in vivo) significantly promoted the viability of HC11 cells and the development of mammary glands by increasing the expression of the proliferative markers cyclin D1/3 and proliferating cell nuclear antigen. However, a high concentration of NaHS (1,000 µM in vitro; 18 mg/kg in vivo) inhibited HC11 cell viability, mammary gland development and the expression levels of proteins involved in proliferation. Subsequent experiments revealed that NaHS regulated the phosphatidylinositol 3­kinase (PI3K)/protein kinase B (Akt)­mammalian target of rapamycin (mTOR) signaling pathway during this process. In vivo, intraperitoneal injection of low concentration NaHS (9 mg/kg) activated the PI3K/Akt­mTOR pathway in mammary glands of pubescent mice, increased the secretion of insulin­like growth factor 1 (IGF­1) and estradiol (E2), and then stimulated mammary gland ductal development. Whereas a high concentration of NaHS (18 mg/kg) elicited the opposite effects to those of low­dose NaHS. In conclusion, the present study demonstrated that exogenous H2S supplied by NaHS may exert bidirectional effects on mammary gland ductal development; promoting ductal development at a low concentration and inhibiting it at a high concentration. The effects of H2S may occur via the intracellular PI3K/Akt­mTOR signaling pathway, or by regulation of the secretion of IGF­1 and E2.

Intraarticular Administration Effect of Hydrogen Sulfide on an In Vivo Rat Model of Osteoarthritis.

Osteoarthritis (OA) is the most common articular chronic disease. However, its current treatment is limited and mostly symptomatic. Hydrogen sulfide (H2S) is an endogenous gas with recognized physiological activities. The purpose here was to evaluate the effects of the intraarticular administration of a slow-releasing H2S compound (GYY-4137) on an OA experimental model. OA was induced in Wistar rats by the transection of medial collateral ligament and the removal of the medial meniscus of the left joint. The animals were randomized into three groups: non-treated and intraarticularly injected with saline or GYY-4137. Joint destabilization induced articular thickening (≈5% increment), the loss of joint mobility and flexion (≈12-degree angle), and increased levels of pain (≈1.5 points on a scale of 0 to 3). Animals treated with GYY-4137 presented improved motor function of the joint, as well as lower pain levels (≈75% recovery). We also observed that cartilage deterioration was attenuated in the GYY-4137 group (≈30% compared with the saline group). Likewise, these animals showed a reduced presence of pro-inflammatory mediators (cyclooxygenase-2, inducible nitric oxide synthase, and metalloproteinase-13) and lower oxidative damage in the cartilage. The increment of the nuclear factor-erythroid 2-related factor 2 (Nrf-2) levels and Nrf-2-regulated gene expression (≈30%) in the GYY-4137 group seem to be underlying its chondroprotective effects. Our results suggest the beneficial impact of the intraarticular administration of H2S on experimental OA, showing a reduced cartilage destruction and oxidative damage, and supporting the use of slow H2S-producing molecules as a complementary treatment in OA.

H2S- and NO-releasing gasotransmitter platform: A crosstalk signaling pathway in the treatment of acute kidney injury.

Acute kidney injury (AKI) is a syndrome affecting most patients hospitalized due to kidney disease; it accounts for 15 % of patients hospitalized in intensive care units worldwide. AKI is mainly caused by ischemia and reperfusion (IR) injury, which temporarily obstructs the blood flow, increases inflammation processes and induces oxidative stress. AKI treatments available nowadays present notable disadvantages, mostly for patients with other comorbidities. Thus, it is important to investigate different approaches to help minimizing side effects such as the ones observed in patients subjected to the aforementioned treatments. Therefore, the aim of the current review is to highlight the potential of two endogenous gasotransmitters - hydrogen sulfide (H2S) and nitric oxide (NO) - and their crosstalk in AKI treatment. Both H2S and NO are endogenous signalling molecules involved in several physiological and pathophysiological processes, such as the ones taking place in the renal system. Overall, these molecules act by decreasing inflammation, controlling reactive oxygen species (ROS) concentrations, activating/inactivating pro-inflammatory cytokines, as well as promoting vasodilation and decreasing apoptosis, hypertrophy and autophagy. Since these gasotransmitters are found in gaseous state at environmental conditions, they can be directly applied by inhalation, or in combination with H2S and NO donors, which are compounds capable of releasing these molecules at biological conditions, thus enabling higher stability and slow release of NO and H2S. Moreover, the combination between these donor compounds and nanomaterials has the potential to enable targeted treatments, reduce side effects and increase the potential of H2S and NO. Finally, it is essential highlighting challenges to, and perspectives in, pharmacological applications of H2S and NO to treat AKI, mainly in combination with nanoparticulated delivery platforms.

Exogenous hydrogen sulfide reduces atrial remodeling and atrial fibrillation induced by diabetes mellitus via activation of the PI3K/Akt/eNOS pathway.

Diabetes mellitus (DM) facilitates atrial fibrosis and increases the risk of atrial fibrillation (AF). The underlying mechanism of DM in causing AF remains mostly unknown and potential therapeutic targets for DM­induced AF are rarely reported. Hydrogen sulfide (H2S) has drawn considerable attention in recent years for its potential as a cardiovascular protector. Thus, the aim of the present study was to investigate the effect of H2S on DM­induced AF and the mechanism of action. Sprague­Dawley rats were divided into four groups, including the control group, the DM group, the H2S group and the DM+H2S group. The DM group and the DM+H2S group were administered streptozotocin to induce DM, whereas the other two groups were given citrate buffer as a control. The H2S group and the DM+H2S group were administered with an intraperitoneal injection of sodium hydrosulfide (precursor of H2S). AF inducibility, AF duration, atrial fibrosis and vital protein expression of oxidative stress were compared among the four groups. The DM group showed significantly higher AF incidence rates and duration (P<0.05). Histology results demonstrated severe atrial fibrosis in the DM group, and the PI3K/Akt/endothelial nitric oxide synthase (eNOS) pathway was significantly downregulated (P<0.05). However, when H2S was administered, the rats showed lower AF incidence and duration compared with the DM group. Additionally, H2S was able to mitigate the atrial fibrosis induced by DM, as well as the proliferation and migration of cardiac fibroblasts, as demonstrated by an MTT assay and real­time cell analyzer migration experiment. Western blotting showed that the expression levels of the PI3K/Akt/eNOS pathway in the DM+H2S group were significantly upregulated compared with those of the DM group (P<0.05). In summary, DM status can lead to the structural remodeling of atrial fibrosis, facilitating AF incidence and persistence. Administration of H2S does not affect the glucose level, but can significantly mitigate atrial fibrosis and reduce the incidence of AF induced by DM, probably via activation of the PI3K/Akt/eNOS pathway.

Hydrogen Sulfide Alleviates Anxiety, Motor, and Cognitive Dysfunctions in Rats with Maternal Hyperhomocysteinemia via Mitigation of Oxidative Stress.

Hydrogen sulfide (H2S) is endogenously produced from sulfur containing amino acids, including homocysteine and exerts neuroprotective effects. An increase of homocysteine during pregnancy impairs fetal growth and development of the offspring due to severe oxidative stress. We analyzed the effects of the H2S donor-sodium hydrosulfide (NaHS) administered to female rats with hyperhomocysteinemia (hHcy) on behavioral impairments and levels of oxidative stress of their offspring. Rats born from females fed with control or high methionine diet, with or without H2S donor injections were investigated. Rats with maternal hHcy exhibit increased levels of total locomotor activity and anxiety, decreased muscle endurance and motor coordination, abnormalities of fine motor control, as well as reduced spatial memory and learning. Oxidative stress in brain tissues measured by activity of glutathione peroxidases and the level of malondialdehyde was higher in rats with maternal hHcy. Concentrations of H2S and the activity and expression of the H2S generating enzyme-cystathionine-beta synthase-were lower compared to the control group. Administration of the H2S donor to females with hHcy during pregnancy prevented behavioral alterations and oxidative stress of their offspring. The acquisition of behavioral together with biochemical studies will add to our knowledge about homocysteine neurotoxicity and proposes H2S as a potential agent for therapy of hHcy associated disorders.

The Effect of a Fast-Releasing Hydrogen Sulfide Donor on Vascularization of Subcutaneous Scaffolds in Immunocompetent and Immunocompromised Mice.

Islet transplantation into subcutaneous polymer scaffolds has shown to successfully induce normoglycemia in type 1 diabetes models. Vascularization of these scaffolds is imperative for optimal control of glucose levels. We studied the effect of the vascular stimulator hydrogen sulfide (H2S) on the degree of vascularization of a scaffold and the role of the immune system in this process. Scaffolds were subcutaneously implanted in immunocompetent C57BL/6 and immunocompromised nude mice. Mice received twice-daily intraperitoneal injections of the fast-releasing H2S donor sodium hydrosulfide (NaHS, 25 or 50 µmol/kg) or saline for 28 days. After 63 days the vascular network was analyzed by histology and gene expression. Here we showed that the vascularization of a subcutaneous scaffold in nude mice was significantly impaired by H2S treatment. Both the CD31 gene and protein expression were reduced in these scaffolds compared to the saline-treated controls. In C57BL/6 mice, the opposite was found, the vascularization of the scaffold was significantly increased by H2S. The mRNA expression of the angiogenesis marker CD105 was significantly increased compared to the controls as well as the number of CD31 positive blood vessels. In conclusion, the immune system plays an important role in the H2S mediated effect on vascularization of subcutaneous scaffolds.

Hydrogen sulfide attenuates diabetic neuropathic pain through NO/cGMP/PKG pathway and µ-opioid receptor.

IMPACT STATEMENT: There are currently approximately 425 million diabetic patients worldwide, of which approximately 90% of patients with diabetes suffer from neuropathy. Diabetic neuropathic pain (DNP) is a common complication of diabetic neuropathy. Nearly half of the patients hospitalized with diabetes have pain symptoms or symptoms related to neurological injury, and the incidence increases with age and diabetic duration. Anti-DNP analgesics have either limited therapeutic effects or serious side effects or lack of clinical trials, which has limited their application. Physiopathological mechanisms and treatment of DNP remain a significant challenge. The present confirmed that inhalation of H2S may attenuate the diabetic neuropathic pain through NO/cGMP/PKG pathway and µ-opioid receptor. It provides us the animal study foundation for the application of H2S on the treatment of DNP and clarifies some target molecules in the pain modulation of DNP.

Tumor pH-responsive metastable-phase manganese sulfide nanotheranostics for traceable hydrogen sulfide gas therapy primed chemodynamic therapy.

Manganese-based nanomaterials have piqued great interest in cancer nanotheranostics, owing to their excellent physicochemical properties. Here we report a facile wet-chemical synthesis of size-controllable, biodegradable, and metastable γ-phase manganese sulfide nanotheranostics, which is employed for tumor pH-responsive traceable gas therapy primed chemodynamic therapy (CDT), using bovine serum albumin (BSA) as a biological template (The final product was denoted as MnS@BSA). The as-prepared MnS@BSA can be degraded in response to the mildly acidic tumor microenvironment, releasing hydrogen sulfide (H2S) for gas therapy and manganese ions for magnetic resonance imaging (MRI) and CDT. In vitro experiments validated the pH-responsiveness of MnS@BSA at pH 6.8 and both H2S gas and •OH radicals were detected during its degradation. In vivo experiments showed efficiently tumor turn-on T1-weighted MRI, significantly suppressed tumor growth and greatly prolonged survival of tumor-bearing mice following intravenous administration of MnS@BSA. Our findings indicated that MnS@BSA nanotheranostics hold great potential for traceable H2S gas therapy primed CDT of cancer.

Dose-Dependent Effects of Long-Term Administration of Hydrogen Sulfide on Myocardial Ischemia-Reperfusion Injury in Male Wistar Rats: Modulation of RKIP, NF-κB, and Oxidative Stress.

Decreased circulating levels of hydrogen sulfide (H2S) are associated with higher mortality following myocardial ischemia. This study aimed at determining the long-term dose-dependent effects of sodium hydrosulfide (NaSH) administration on myocardial ischemia-reperfusion (IR) injury. Male rats were divided into control and NaSH groups that were treated for 9 weeks with daily intraperitoneal injections of normal saline or NaSH (0.28, 0.56, 1.6, 2.8, and 5.6 mg/kg), respectively. At the end of the study, hearts from all rats were isolated and hemodynamic parameters were recorded during baseline and following IR. In isolated hearts, infarct size, oxidative stress indices as well as mRNA expression of H2S-, nitric oxide (NO)-producing enzymes, and inflammatory markers were measured. In heart tissue following IR, low doses of NaSH (0.28 and 0.56 mg/kg) had no effect, whereas an intermediate dose (1.6 mg/kg), improved recovery of hemodynamic parameters, decreased infarct size, and decreased oxidative stress. It also increased expression of cystathionine γ-lyase (CSE), Raf kinase inhibitor protein (RKIP), endothelial NO synthase (eNOS), and neuronal NOS (nNOS), as well as decreased expression of inducible NOS (iNOS) and nuclear factor kappa-B (NF-κB). At the high dose of 5.6 mg/kg, NaSH administration was associated with worse recovery of hemodynamic parameters and increased infarct size as well as increased oxidative stress. This dose also decreased expression of CSE, RKIP, and eNOS and increased expression of iNOS and NF-κB. In conclusion, chronic treatment with NaSH has a U-shaped concentration effect on IR injury in heart tissue. An intermediate dose was associated with higher CSE-derived H2S, lower iNOS-derived NO, lower oxidative stress, and inflammation in heart tissue following IR.