Inhalation of hydrogen gas attenuates brain injury in mice with cecal ligation and puncture via inhibiting neuroinflammation, oxidative stress and neuronal apoptosis

Molecular hydrogen mitigates traumatic brain injury-induced lung injury via NLRP3 inflammasome inhibition

INTRODUCTION

Hydrogen gas has demonstrated significant antioxidant and anti-inflammatory properties, suggesting potential therapeutic benefits in TBI.

METHODS

We subjected to controlled cortical impact in mice to construct TBI model. They received an intraperitoneal injection of MCC950, a selective NLRP3 inhibitor, at 10 mg/kg 30 min before TBI. Inhalation of 2% H2 is adopted in TBI mice for 60 min, starting 1 and 6 h post-TBI. 24 h after H2 inhalation, we extracted tissues and analyzed injury related changes. The H2 levels in arterial and venous were tracked after inhalation. Lung tissue was examined for histopathological changes and apoptosis using H&E and TUNEL assays. The total protein in the BALF, oxygenation index, lung wet-to-dry weight ratio, and lung MPO activity were measured to evaluate the severity of TBI-induced lung injury. Protein and mRNA levels of NLRP3, ASC, Caspase-1, IL-18, and IL-1β in the lung tissue were quantified using western blotting and quantitative PCR. The expression changes and distribution status of NLRP3 and Caspase-1 were examined by immunofluorescence and immunohistochemistry staining.

RESULTS

Significant lung injury at 24 h post-TBI got significantly reduced by treatment of 2% H2. TBI activated the NLRP3 inflammasome, increasing NLRP3, ASC, and caspase-1 levels, to lead to higher IL-1β and IL-18 secretion in the lungs. Blocking NLRP3 reduced lung damage from TBI, and its combination with 2% H2 provided better protection than either treatment alone.

CONCLUSIONS

2% H2 can protect against TBI-induced lung injury by inhibiting NLRP3 inflammasome activation, thereby alleviating inflammation and inhibiting apoptosis.

Cecal slurry-induced sepsis in mice impairs cognition and decreases SUMO-2/3 conjugation

Sepsis is characterized by multiple organ dysfunction, dysregulation of the response to the infection process, and a high mortality rate in intensive care units. In addition, individuals who overcome sepsis often manifest cognitive deficits associated with neuroinflammation resulting from the entry of pro-inflammatory cytokines into the brain. Post-translational protein modifications, such as SUMOylation, can regulate the expression of pro-inflammatory genes during sepsis. Since SUMO-2/3 can play a role in pathological conditions, our aim was to investigate a potential link between sepsis-induced cognitive decline and SUMOylation by this isoform. Firstly, the cecal slurry model was induced by intraperitoneally injecting male Swiss mice with different volumes of a cecal solution. Following assessment of body temperature, mass and septic scores, the groups that received 300 μL and 350 μL of the cecal solution were selected for the behavioural tests, as they presented signs of sepsis without excessive mortality. Surviving animals were evaluated for cognition/memory and anxious/depressive-like behaviours through the open-field, object recognition, Y-maze, and tail suspension tests. Subsequently, SUMO-2/3 conjugation was determined in samples from the hippocampus and prefrontal cortex by Western blotting. Mice in the septic groups showed decreased locomotor activity, anxious-and depressive-like behaviours, as well as impaired memory. These deficits were accompanied by a decrease in SUMO-2/3 conjugation in the hippocampus and prefrontal cortex at 24 h and 10 days after the induction of the cecal slurry model. Taken together, our findings suggest that SUMOylation is impaired in septic animals and this could be related to the behavioural deficits seen in the surviving mice.

Can molecular hydrogen supplementation enhance physical performance in healthy adults? A systematic review and meta-analysis

Background

Physical exertion during exercise often leads to increased oxidative stress and inflammatory responses, significantly affecting physical performance. Current strategies to mitigate these effects are limited by their effectiveness and potential side effects. Molecular hydrogen (H₂) has gained attention for its antioxidant and anti-inflammatory properties. Studies have suggested that H2 supplementation contributes to antioxidant potential and anti-fatigue during exercise, but the variance in the observations and study protocols is presented across those studies.

Objective

This systematic review and meta-analysis aimed to comprehensively characterize the effects of H₂ supplementation on physical performance (i.e., endurance, muscular strength, and explosive power), providing knowledge that can inform strategies using H2 for enhancing physical performance.

Methods

We conducted a literature search of six databases (PubMed, Web of Science, Medline, Sport-Discus, Embase, and PsycINFO) according to the PRISMA guidelines. The data were extracted from the included studies and converted into the standardized mean difference (SMD). After that, we performed random-effects meta-analyses and used the I 2 statistic to evaluate heterogeneity. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) was used to assess the quality of the evidence obtained from this meta-analysis.

Results

In total, 27 publications consisting of 597 participants were included. The search finally included aerobic endurance, anaerobic endurance, muscular strength, lower limb explosive power, rating of perceived exertion (RPE), blood lactate (BLA), and average heart rate (HRavg) in the effect size (ES) synthesis. The ES of H2 on aerobic endurance, including V̇O2max (SMD = 0.09, p = 0.394; I 2 = 0%) and aerobic endurance exercise (SMD = 0.04, p = 0.687; I 2 = 0%), were not significant and trivial; the ES of H2 on 30 s maximal anaerobic endurance (SMD = 0.19, p = 0.239; I 2 = 0%) was not significant and trivial; the ES of H2 on muscular strength (SMD = 0.19, p = 0.265; I 2 = 0%) was not significant and trivial; but the ES of H2 on lower limb explosive power (SMD = 0.30, p = 0.018; I 2 = 0%) was significant and small. In addition, H2 reduces RPE (SMD = -0.37, p = 0.009; I 2 = 58.0%) and BLA (SMD = -0.37, p = 0.001; I 2 = 22.0%) during exercise, but not HRavg (SMD = -0.27, p = 0.094; I 2 = 0%).

Conclusion

These findings suggest that H2 supplementation is favorable in healthy adults to improve lower limb explosive power, alleviate fatigue, and boost BLA clearance, but may not be effectively improving aerobic and anaerobic endurance and muscular strength. Future studies with more rigorous designs are thus needed to examine and confirm the effects of H2 on these important functionalities in humans.

Systematic review registration

http://www.crd.york.ac.uk/PROSPERO.

HYDROGEN PREVENTS LIPOPOLYSACCHARIDE-INDUCED PULMONARY MICROVASCULAR ENDOTHELIAL CELL INJURY BY INHIBITING STORE-OPERATED Ca 2+ ENTRY REGULATED BY STIM1/ORAI1

ABSTRACT

Background: Sepsis is a type of life-threatening organ dysfunction that is caused by a dysregulated host response to infection. The lung is the most vulnerable target organ under septic conditions. Pulmonary microvascular endothelial cells (PMVECs) play a critical role in acute lung injury (ALI) caused by severe sepsis. The impairment of PMVECs during sepsis is a complex regulatory process involving multiple mechanisms, in which the imbalance of calcium (Ca 2+ ) homeostasis of endothelial cells is a key factor in its functional impairment. Our preliminary results indicated that hydrogen gas (H 2 ) treatment significantly alleviates lung injury in sepsis, protects PMVECs from hyperpermeability, and decreases the expression of plasma membrane stromal interaction molecule 1 (STIM1), but the underlying mechanism by which H 2 maintains Ca 2+ homeostasis in endothelial cells in septic models remains unclear. Thus, the purpose of the present study was to investigate the molecular mechanism of STIM1 and Ca 2+ release-activated Ca 2+ channel protein1 (Orai1) regulation by H 2 treatment and explore the effect of H 2 treatment on Ca 2+ homeostasis in lipopolysaccharide (LPS)-induced PMVECs and LPS-challenged mice. Methods: We observed the role of H 2 on LPS-induced ALI of mice in vivo . The lung wet/dry weight ratio, total protein in the bronchoalveolar lavage fluid, and Evans blue dye assay were used to evaluate the pulmonary endothelial barrier damage of LPS-challenged mice. The expression of STIM1 and Orai1 was also detected using epifluorescence microscopy. Moreover, we also investigated the role of H 2 -rich medium in regulating PMVECs under LPS treatment, which induced injury similar to sepsis in vitro . The expression of STIM1 and Orai1 as well as the Ca 2+ concentration in PMVECs was examined. Results:In vivo , we found that H 2 alleviated ALI of mice through decreasing lung wet/dry weight ratio, total protein in the bronchoalveolar lavage fluid and permeability of lung. In addition, H 2 also decreased the expression of STIM1 and Orai1 in pulmonary microvascular endothelium. In vitro , LPS treatment increased the expression levels of STIM1 and Orai1 in PMVECs, while H 2 reversed these changes. Furthermore, H 2 ameliorated Ca 2+ influx under sepsis-mimicking conditions. Treatment with the sarco/endoplasmic reticulum Ca 2+ adenosine triphosphatase inhibitor, thapsigargin, resulted in a significant reduction in cell viability as well as a reduction in the expression of junctional proteins, including vascular endothelial-cadherin and occludin. Treatment with the store-operated Ca 2+ entry inhibitor, YM-58483 (BTP2), increased the cell viability and expression of junctional proteins. Conclusions: The present study suggested that H 2 treatment alleviates LPS-induced PMVEC dysfunction by inhibiting store-operated Ca 2+ entry mediated by STIM1 and Orai1 in vitro and in vivo .

The Molecular Biological Mechanism of Hydrogen Therapy and Its Application in Spinal Cord Injury

Hydrogen, which is a novel biomedical molecule, is currently the subject of extensive research involving animal experiments and in vitro cell experiments, and it is gradually being applied in clinical settings. Hydrogen has been proven to possess anti-inflammatory, selective antioxidant, and antiapoptotic effects, thus exhibiting considerable protective effects in various diseases. In recent years, several studies have provided preliminary evidence for the protective effects of hydrogen on spinal cord injury (SCI). This paper provides a comprehensive review of the potential molecular biology mechanisms of hydrogen therapy and its application in treating SCI, with an aim to better explore the medical value of hydrogen and provide new avenues for the adjuvant treatment of SCI.

Sepsis sensitizes behavioural amphetamine responses while inducing inflammatory and neurotrophic vulnerability in the cecal ligation and puncture model

The present study aimed to evaluate if sepsis sensitizes behavioural and biochemical responses induced by m-amphetamine. For this, Wistar rats were submitted to the cecal ligation and puncture. After 30 days of cecal ligation and puncture procedure, the animals were submitted to a single intraperitoneal injection of saline or m-amphetamine (.25, .50, or 1.0 mg/kg). Locomotor behaviour was assessed 2 h after the administration. Interleukin (IL)-1β, IL-6, IL-10, tumour necrosis factor-α, dopamine-cAMP-regulated phosphoprotein of 32,000 kDa (DARPP-32) and neuronal calcium sensor (NCS-1) levels were evaluated in the frontal cortex, hippocampus and striatum. Also, brain-derived neurotrophic factor (BDNF), neuronal growth factor and glial-derived neurotrophic factor levels were assessed in the hippocampus. M-amphetamine alone (.25 and 1.0 mg/kg) increased rats' locomotion and exploratory behaviour compared with the Sham + Sal. Animals from the cecal ligation and puncture + m-amphetamine (.5 and/or 1.0 mg/kg) group showed an increase in locomotion, exploratory and risk-like behaviour when compared with the Sham + Saline group and with its respective Sham groups. Cecal ligation and puncture increased interleukin levels compared with the Sham + Sal. However, cecal ligation and puncture animals that received m-amphetamine (1 mg/kg) increased even more, these inflammatory parameters compared with the Sham + Sal and the cecal ligation and puncture + saline group. M-amphetamine at lower doses increased neurotrophic factors, but higher doses decreased these parameters in the brain of cecal ligation and puncture rats. M-amphetamine dose-dependently increased DARPP-32 and NCS-1 levels in cecal ligation and puncture rats in some structures. In conclusion, these results demonstrate that sepsis sensitizes behavioural amphetamine responses while inducing inflammatory and neurotrophic vulnerability in the cecal ligation and puncture model.

Effects of the PI3K/Akt/HO-1 pathway on autophagy in a sepsis-induced acute lung injury mouse model

Sepsis-induced lung injury is an acute hypoxic respiratory insufficiency caused by systemic infectious factors that results in alveolar epithelial cell and capillary endothelial cell injury, diffuse pulmonary interstitial edema, and alveolar edema. Heme oxygenase (HO)-1 is usually associated with inflammation and has anti-inflammatory effects. Autophagy is a degradation pathway that eliminates cellular metabolic waste and plays an important protective role during stress. The phosphatidylinositol 3-kinase/ protein kinase B (PI3K/Akt) signaling pathway plays a key role in mediating cellular responses to inflammatory reactions. Therefore, we hypothesized that HO-1 is associated with autophagy and regulated by the PI3K/Akt signaling pathway in mice with sepsis-induced lung injury. Sepsis-induced lung injury was induced in mice using cecal ligation and puncture (CLP). Hemin or Sn-protoporphyrin IX (SnPP) was administered via intraperitoneal injection before surgery. Survival rates were observed during days 1-7 after the surgery; lung histology was discerned 24 h after the surgery; pro-inflammatory and anti-inflammatory factors in plasma and lung tissue were measured using enzyme-linked immunosorbent assay (ELISA); HO-1, Beclin-1, microtubule-associated protein 1 light chain 3B (LC3B)-II, p62 and lysosome associated membrane protein (LAMP)2 protein expression levels were measured 24 h after the surgery; HO-1 and LC3B-II protein expression levels were observed using immunofluorescence 24 h after the surgery; and autophagosomes were detected using electron microscopy 24 h after the surgery. Furthermore, when PI3K inhibitors LY294002, PI3K activators Recilisib and hemin were administered before the surgery, Akt, p-Akt, HO-1, and LC3-II levels were measured 24 h post-surgery. We found that HO-1 overexpression increased the survival rate and inhibited sepsis-induced lung injury. HO-1 overexpression attenuated the levels of proinflammatory cytokines (TNF-α, IL-1β) and increased the anti-inflammatory cytokine (IL-10, HO-1) overexpression. Moreover, HO-1 overexpression was also associated with increased expression of Beclin-1, LC3B-II and LAMP2 protein expression; decreased p62 protein expression; and significantly increased autophagosome formation. The results for HO-1-downregulated mice contrasted with those mentioned above. LY294002 inhibited p-Akt/Akt, HO-1, and LC3B-II protein expression; and hemin reversed the inhibitory effect of LY294002. The protective effect of HO-1 was involved in the mediation of autophagy, which may be regulated by the PI3K/Akt signaling pathway during sepsis-induced lung injury in mice.

Research progress on antisepsis effect of apigenin and its mechanism of action

Sepsis is an abnormal immune response to infections and can trigger MODS. Despite the availability of advanced clinical techniques and monitoring methods, the mortality rate of the disease is still high, posing a heavy burden to patients and the whole society. Hence, the research on novel drugs and targets is particularly important. As a natural phyto-flavonoid, apigenin boasts anti-inflammatory, antioxidant, anti-cancer, anti-viral, and anti-bacterial effects. Besides, in-vitro experiments and animal models have also revealed the crucial role of apigenin in the treatment of infectious diseases and sepsis. In this context, this paper reviews the pharmacological activity and underlying mechanisms of action of apigenin in sepsis treatment and organ protection, as well as the potential apigenin-based therapeutic strategies against sepsis. Therefore, this review will shed new light on the scientific research and clinical treatment of sepsis.

Two flavonoids, baicalein and naringin, are effective as anti-inflammatory and anti-oxidant agents in a rat model of polymicrobial sepsis

INTRODUCTION

In this study, our aim was to investigate the possible protective and therapeutic effects of these two flavonoids, baicalein, and naringin, in 50 and 100 mg/kg doses applied both before and after cecal ligation and puncture (CLP) procedures in a polymicrobial sepsis rat model, and evaluate the possible contribution of oxidative and inflammatory markers by immunological, biochemical, molecular, and histopathological methods.

METHODS

Sixty-six Wistar albino rats were divided into 11 groups. The pro-inflammatory (TNF-alpha, IL-1-beta, and IL-6) and anti-inflammatory (TGF-beta and IL-10) cytokine levels were measured by ELISA technique. CD3, CD68, and nuclear factor kappa B positivity rates were detected by immunohistochemical methods. Oxidative stress parameters (MDA, SOD, and GSH) were measured by tissue biochemistry.

RESULTS

Sepsis caused a significant increase in all pro-inflammatory cytokine levels and MDA activity. Also, it led to an increase in the positivities of CD3, CD68, and NF-κB markers. However, especially pre-CLP doses of baicalein and naringin inhibited the inflammation process by suppressing pro-inflammatory and increasing anti-inflammatory cytokine levels, as well as regulating the oxidative stress process by normalizing the oxidant/anti-oxidant enzyme levels.

CONCLUSION

Both pre- and post-application of baicalein and naringin are quite effective to prevent sepsis-caused cellular processes. This protective and therapeutic effects by baicalein and naringin in animals with sepsis seems to be originated from the high antioxidant capacity and inhibition of pro-inflammatory cytokine production. Thus, those natural agents may prove to be valuable protective agent against septic shock.

Hydrogen alleviated cognitive impairment and blood‒brain barrier damage in sepsis-associated encephalopathy by regulating ABC efflux transporters in a PPARα-dependent manner

Hydrogen (H₂) can protect against blood‒brain barrier (BBB) damage in sepsis-associated encephalopathy (SAE), but the mechanism is still unclear. We examined whether it is related to PPARα and its regulatory targets, ABC efflux transporters. After injection with DMSO/GW6471 (a PPARα inhibitor), the mice subjected to sham/caecal ligation and puncture (CLP) surgery were treated with H₂ for 60 min postoperation. Additionally, bEnd.3 cells were grown in DMSO/GW6471-containing or saline medium with LPS. In addition to the survival rates, cognitive function was assessed using the Y-maze and fear conditioning tests. Brain tissues were stained with TUNEL and Nissl staining. Additionally, inflammatory mediators (TNF-α, IL-6, HMGB1, and IL-1β) were evaluated with ELISA, and PPARα, ZO-1, occludin, VE-cadherin, P-gp, BCRP and MRP2 were detected using Western blotting. BBB destruction was assessed by brain water content and Evans blue (EB) extravasation. Finally, we found that H₂ improved survival rates and brain dysfunction and decreased inflammatory cytokines. Furthermore, H₂ decreased water content in the brain and EB extravasation and increased ZO-1, occludin, VE-cadherin and ABC efflux transporters regulated by PPARα. Thus, we concluded that H₂ decreases BBB permeability to protect against brain dysfunction in sepsis; this effect is mediated by PPARα and its regulation of ABC efflux transporters.

Acute and long-term cognitive impairment following sepsis: mechanism and prevention

INTRODUCTION

Sepsis is a severe host response to infection, which induces both acute and long-term cognitive impairment. Despite its high incidence following sepsis, the underlying mechanisms remain elusive and effective treatments are not available clinically.

AREA COVERED

This review focuses on elucidating the pathological mechanisms underlying cognitive impairment following sepsis. Specifically, the authors discuss the role of systemic inflammation response, blood-brain barrier disruption, neuroinflammation, mitochondrial dysfunction, neuronal dysfunction, and Aβ accumulation and tau phosphorylation in cognitive impairment after sepsis. Additionally, they review current strategies to ameliorate cognitive impairment.

EXPERT OPINION

Potential interventions to reduce cognitive impairment after sepsis include earlier diagnosis and effective infection control, hemodynamic homeostasis, and adequate brain perfusion. Furthermore, interventions to reduce inflammatory response, reactive oxygen species, blood-brain barrier disruption, mitochondrial dysfunction, neuronal injury or death could be beneficial. Implementing strategies to minimize delirium, sleep disturbance, stress factors, and immobility are also recommended. Furthermore, avoiding neurotoxins and implementing early rehabilitation may also be important for preventing cognitive impairment after sepsis.

Conflicting findings on the effectiveness of hydrogen therapy for ameliorating vascular leakage in a 5-day post hypoxic-ischemic survival piglet model

Neonatal hypoxic-ischemic encephalopathy (HIE) is a major cause of morbidity and mortality in newborns in both high- and low-income countries. The important determinants of its pathophysiology are neural cells and vascular components. In neonatal HIE, increased vascular permeability due to damage to the blood-brain barrier is associated with seizures and poor outcomes in both translational and clinical studies. In our previous studies, hydrogen gas (H₂) improved the neurological outcome of HIE and ameliorated the cell death. In this study, we used albumin immunohistochemistry to assess if H₂ inhalation effectively reduced the cerebral vascular leakage. Of 33 piglets subjected to a hypoxic-ischemic insult, 26 piglets were ultimately analyzed. After the insult, the piglets were grouped into normothermia (NT), H₂ ventilation (H₂), therapeutic hypothermia (TH), and H₂ combined with TH (H₂-TH) groups. The ratio of albumin stained to unstained areas was analyzed and found to be lower in the H₂ group than in the other groups, although the difference was not statistically significant. In this study, H₂ therapy did not significantly improve albumin leakage despite the histological images suggesting signs of improvement. Further investigations are warranted to study the efficacy of H₂ gas for vascular leakage in neonatal HIE.

Hydrogen regulates mitochondrial quality to protect glial cells and alleviates sepsis-associated encephalopathy by Nrf2/YY1 complex promoting HO-1 expression

BACKGROUND

Sepsis-associated encephalopathy (SAE) is a complication of the central nervous system in patients with sepsis. Currently, no effective treatment for sepsis is available. Hydrogen plays a protective role in different diseases; however, the detailed mechanism of hydrogen-treated disease remains unclear. The purpose of this study was to investigate the effect of hydrogen on SAE in vitro and in vivo and the mechanism of hydrogen in mitochondrial dynamics and its function in astrocytes and microglia stimulated by lipopolysaccharides (LPSs).

METHODS

Animal models of SAE were generated by cecal ligation and puncture, and the SAE model was established by in vitro LPS stimulation. MTT, lactate dehydrogenase (LDH), reactive oxygen species (ROS), heme oxygenase-1 (HO-1) activity, mitochondrial membrane potential (MMP), and cell apoptosis assays were used to determine the effect of hydrogen on astrocytes and microglia stimulated by LPSs. The relationships between nuclear factor erythroid 2-related factor 2 (Nrf2), YY1, and HO-1 were examined by chromatin immunoprecipitation and co-immunoprecipitation. Mitochondrial homeostasis-related proteins in LPS-stimulated glial cells and brain tissues of SAE mice were detected by western blotting. The effects of hydrogen treatment in the SAE mouse model were investigated using Morris water maze and Y-maze analyses.

RESULTS

After performing experiments with different concentrations of LPSs in vitro, we selected 1000 ng/ml for subsequent experiments. Hydrogen attenuated the increase in ROS, LDH, and apoptosis and promoted decreases in cell activity and MMP, further promoting an increase in HO-1 expression induced by LPSs in astrocytes and microglia. Moreover, hydrogen further promoted the expression of Nrf2, HO-1, PGC-1α, TFAM, PARKIN, and PINK1, inhibited LPS-induced OPA1 and MFN2 expression in astrocytes and microglia, and downregulated the expression of DRP1 after LPS induction. Intriguingly, hydrogen treatment enhanced the binding between Nrf2 and YY1. However, silencing Nrf2 or YY1 abolished the protective effects of hydrogen on cell activity, LDH, ROS, and MMP; apoptosis; and regulation of Nrf2, HO-1, PGC-1α, TFAM, OPA1, DRP1, MFN2, PARKIN, and PINK1 in microglia. Finally, hydrogen treatment improved the results of behavioral detection, apoptosis, Nrf2, HO-1, PGC-1α, TFAM, OPA1, DRP1, MFN2, PARKIN, PINK1, and cytokines in SAE in vivo.

CONCLUSIONS

Hydrogen improved cell injury and mitochondrial quality, which were associated with HO-1 expression promoted by the Nrf2/YY1 complex in vitro. Thus, hydrogen treatment may represent a novel therapeutic method for treating SAE.

Effects of molecular hydrogen supplementation on fatigue and aerobic capacity in healthy adults: A systematic review and meta-analysis

Background

Fatigue is oftentimes induced by high-intensity exercise potentially via the exceeded amount of reactive oxygen species, leading to diminished functions (e.g., aerobic capacity) and increased risk of injuries. Studies indicate that molecular hydrogen (H₂), with antioxidant and anti-inflammatory properties, may be a promising strategy to alleviate fatigue and improve aerobic capacity. However, such effects have not been comprehensively characterized.

Objective

To systematically assess the effects of in taking H₂ on fatigue and aerobic capacity in healthy adults.

Methods

The search was conducted in August 2022 in five databases. Studies with randomized controlled or crossover designs that investigated the rating of perceived exertion (RPE), maximal oxygen uptake (VO_2max), peak oxygen uptake (VO_2peak), and endurance performance were selected. The data (mean ± standard deviation and sample size) were extracted from the included studies and were converted into the standardized mean difference (SMD). Random-effects meta-analyses were performed. Subgroup analysis was used to analyze potential sources of heterogeneity due to intervention period, training status, and type of exercise.

Results

Seventeen publications (19 studies) consisting of 402 participants were included. The pooled effect sizes of H₂ on RPE (SMD_pooled = -0.38, 95%CI -0.65 to -0.11, p = 0.006, I ² = 33.6%, p = 0.149) and blood lactate (SMD_pooled = -0.42, 95% CI -0.72 to -0.12, p = 0.006, I ² = 35.6%, p = 0.114) were small yet significant with low heterogeneity. The pooled effect sizes of H₂ on VO_2max and VO_2peak (SMD_pooled = 0.09, 95% CI -0.10 to 0.29, p = 0.333, I ² = 0%, p = 0.998) and endurance performance (SMD_pooled = 0.01, 95% CI -0.23 to 0.25, p = 0.946, I ² = 0%, p > 0.999) were not significant and trivial without heterogeneity. Subgroup analysis revealed that the effects of H₂ on fatigue were impacted significantly by the training status (i.e., untrained and trained), period of H₂ implementation, and exercise types (i.e., continuous and intermittent exercises).

Conclusions

This meta-analysis provides moderate evidence that H₂ supplementation alleviates fatigue but does not enhance aerobic capacity in healthy adults.

Systematic review registration

www.crd.york.ac.uk/PROSPERO/, identifier: CRD42022351559.

Impact of hydrogen gas inhalation during therapeutic hypothermia on cerebral hemodynamics and oxygenation in the asphyxiated piglet

We previously reported the neuroprotective potential of combined hydrogen (H2) gas ventilation therapy and therapeutic hypothermia (TH) by assessing the short-term neurological outcomes and histological findings of 5-day neonatal hypoxic-ischemic (HI) encephalopathy piglets. However, the effects of H2 gas on cerebral circulation and oxygen metabolism and on prognosis were unknown. Here, we used near-infrared time-resolved spectroscopy to compare combined H2 gas ventilation and TH with TH alone. Piglets were divided into three groups: HI insult with normothermia (NT, n = 10), HI insult with hypothermia (TH, 33.5 ± 0.5 °C, n = 8), and HI insult with hypothermia plus H2 ventilation (TH + H2, 2.1-2.7%, n = 8). H2 ventilation and TH were administered and the cerebral blood volume (CBV) and cerebral hemoglobin oxygen saturation (ScO2) were recorded for 24 h after the insult. CBV was significantly higher at 24 h after the insult in the TH + H2 group than in the other groups. ScO2 was significantly lower throughout the 24 h after the insult in the TH + H2 group than in the NT group. In conclusion, combined H2 gas ventilation and TH increased CBV and decreased ScO2, which may reflect elevated cerebral blood flow to meet greater oxygen demand for the surviving neurons, compared with TH alone.

Molecular hydrogen attenuates sepsis-induced cognitive dysfunction through regulation of tau phosphorylation

BACKGROUND

Sepsis-associated encephalopathy (SAE) is a cognitive dysfunction caused by sepsis. Hyperphosphorylated tau is considered to play a significant role in the progression of neurodegenerative disease and also contributes to cognitive dysfunction in septic mice. Molecular hydrogen (H₂) plays an antioxidant and anti-inflammatory role, and plays a protective role in septic mice. This study explored the possible effects of H₂ on cognition and tau phosphorylation in a mouse model of SAE.

METHODS

The model of sepsis was established in C57BL/6J male mice by cecal ligation and puncture surgery. Mice treated with 2 % H₂ inhalation for 60 min at 1 h and 6 h after surgery, respectively. HY-15769, the inhibitor of Tau Tubulin Kinase 1 (TTBK1), was injected 1 h before the surgery. The 7-day survival rates of the mice were recorded. Cognitive behavior was tested with both novel object recognition and the Y-maze novelty arm recognition on day 7 after surgery. Hematoxylin-eosin staining was used to observe the histological damage in CA1 region of hippocampus. The expression of inflammatory factors in hippocampus was assessed by Elisa. Western blotting was adopted to determine the tau phosphorylation levels at AT8 epitopes (pSer202 and pThr205) and T22 epitopes (neurofibrillary tangle protein oligomer), and the GSK3β phosphorylation levels (Tyr216), as well as p-Ser422 and TTBK1 levels in the hippocampus. The number of dendritic spine and mushroom type of dendritic spines in the hippocampus were assessed by Golgi staining.

RESULTS

The survival rate, visual and spatial learning ability, and memory ability were improved in septic mice treated with H₂. After H₂ treatment, the density of dendritic spine, mushroom type of dendritic spine, and the number of normal hippocampal neurons were progressively elevated. H₂ decreased the levels of phosphorylated tau protein, tau oligomer and TTBK1, as well as the phosphorylation of tau key kinase. Furthermore, the injection of HY-15769 (a TTBK1 inhibitor) protected SAE through the similar way.

CONCLUSION

The protective effect of H₂ on cognitive dysfunction induced by SAE may be achieved by inhibiting tau phosphorylation, which is perhaps related with the inhibition of TTBK1.

P2X7 receptor contributes to long-term neuroinflammation and cognitive impairment in sepsis-surviving mice

Introduction: Sepsis is defined as a multifactorial debilitating condition with high risks of death. The intense inflammatory response causes deleterious effects on the brain, a condition called sepsis-associated encephalopathy. Neuroinflammation or pathogen recognition are able to stress cells, resulting in ATP (Adenosine Triphosphate) release and P2X7 receptor activation, which is abundantly expressed in the brain. The P2X7 receptor contributes to chronic neurodegenerative and neuroinflammatory diseases; however, its function in long-term neurological impairment caused by sepsis remains unclear. Therefore, we sought to evaluate the effects of P2X7 receptor activation in neuroinflammatory and behavioral changes in sepsis-surviving mice. Methods: Sepsis was induced in wild-type (WT), P2X7^-/-, and BBG (Brilliant Blue G)-treated mice by cecal ligation and perforation (CLP). On the thirteenth day after the surgery, the cognitive function of mice was assessed using the novel recognition object and Water T-maze tests. Acetylcholinesterase (AChE) activity, microglial and astrocytic activation markers, and cytokine production were also evaluated. Results: Initially, we observed that both WT and P2X7^-/- sepsis-surviving mice showed memory impairment 13 days after surgery, once they did not differentiate between novel and familiar objects. Both groups of animals presented increased AChE activity in the hippocampus and cerebral cortex. However, the absence of P2X7 prevented partly this increase in the cerebral cortex. Likewise, P2X7 absence decreased ionized calcium-binding protein 1 (Iba^-1) and glial fibrillary acidic protein (GFAP) upregulation in the cerebral cortex of sepsis-surviving animals. There was an increase in GFAP protein levels in the cerebral cortex but not in the hippocampus of both WT and P2X7^-/- sepsis-surviving animals. Pharmacological inhibition or genetic deletion of P2X7 receptor attenuated the production of Interleukin-1β (IL-1β), Tumor necrosis factor-α (TNF-α), and Interleukin-10 (IL-10). Conclusion: The modulation of the P2X7 receptor in sepsis-surviving animals may reduce neuroinflammation and prevent cognitive impairment due to sepsis-associated encephalopathy, being considered an important therapeutic target.

Hydrogen Gas Treatment Improves Postoperative Delirium and Cognitive Dysfunction in Elderly Noncardiac Patients

Purpose: Postoperative delirium is a state of acute brain dysfunction characterized by fluctuating mental status that affects millions of patients each year. We used prophylactic inhalation of hydrogen gas in elderly patients undergoing elective surgery to compare their occurrence of postoperative delirium with that of controls. Methods: A total of 184 patients aged ≥ 65 years were enrolled and randomized into either a control group or a hydrogen inhalation group. The quality of sleep was assessed 1 day before and 1, 3, and 7 days after surgery at 8 A.M. The Confusion Assessment Method (CAM) was used as a screening tool for delirium and assessed the patients’ state of consciousness 1−7 days after surgery. Results: Postoperative delirium occurred in 17 (24%) of 70 patients without hydrogen inhalation and in 10 (12%) of 83 patients after hydrogen inhalation. The incidence of delirium was decreased in the hydrogen group. No significant differences were found between length of stay in hospital after surgery and sleep quality at 1, 3, and 7 days postoperatively between the two groups. The numerical rating scale (NRS) pain scores were higher in the hydrogen group (4.08 ± 1.77) than the control group (3.54 ± 1.77) on day 1 (p < 0.05); however, the mean difference between the two groups was small (1 to 1.6). There were no significant differences on day 3 and 7. The postoperative C-reactive protein level was significantly lower in the hydrogen group than the control group. Conclusions: This study suggests that hydrogen inhalation can prevent postoperative delirium in elderly noncardiac patients by reducing the inflammatory response.

Effect of molecular hydrogen treatment on Sepsis-Associated encephalopathy in mice based on gut microbiota

INTRODUCTION

In our experiments, male wild-type mice were randomly divided into four groups: the sham, SAE, SAE + 2% hydrogen gas inhalation (H₂ ), and SAE + hydrogen-rich water (HW) groups. The feces of the mice were collected for 16 S rDNA analysis 24 h after the models were established, and the serum and brain tissue of the mice were collected for nontargeted metabolomics analysis.

AIM

Destruction of the intestinal microbiota is a risk factor for sepsis and subsequent organ dysfunction, and up to 70% of severely ill patients with sepsis exhibit varying degrees of sepsis-associated encephalopathy (SAE). The pathogenesis of SAE remains unclear. We aimed to explore the changes in gut microbiota in SAE and the regulatory mechanism of molecular hydrogen.

RESULTS

Molecular hydrogen treatment significantly improved the functional outcome of SAE and downregulated inflammatory reactions in both the brain and the gut. In addition, molecular hydrogen treatment improved gut microbiota dysbiosis and partially amended metabolic disorder after SAE.

CONCLUSIONS

Molecular hydrogen treatment promotes functional outcomes after SAE in mice, which may be attributable to increasing beneficial bacteria, repressing harmful bacteria, and metabolic disorder, and reducing inflammation.

Amarogentin has protective effects against sepsis-induced brain injury via modulating the AMPK/SIRT1/NF-κB pathway

Amarogentin (AMA), a secoiridoid glycoside that is mainly derived from SwertiaandGentiana roots, has been confirmed to exhibit antioxidative, tumor-suppressive and anti-diabetic properties. This research intends to investigate the protective effect of AMA against sepsis-induced brain injury and its mechanism. NSC-34 and HT22 cells were treated with lipopolysaccharide (LPS) to induce an in-vitro sepsis model and then treated with varying concentrations (1, 5, 10 µM) of AMA. Cell proliferation and apoptosis were evaluated. The intensity of inflammation and oxidative stress were assessed by different methods. The AMPK/SIRT1/NF-κB pathway expression was determined by WB. An in-vitro sepsis model was set up with cecal ligation and puncture (CLP) in adult C57/BL6J mice, and different concentrations (25, 50, 100 mg/kg) of AMA were applied for treatment. Neurological function was evaluated using the modified neurological severity scores (mNSS), and the brain tissue damage was measured using hematoxylin-eosin (H&E) staining and Nissl staining. Tissue apoptosis was tested using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. Then, the AMPK inhibitor Compound C (CC) was administered to confirm AMA-mediated mechanism. Our finding illustrated that AMA mitigated LPS-induced neuronal damage, inflammation and oxidative stress, activated the AMPK/SIRT1 pathway and choked NF-κB phosphorylation. Furthermore, AMA improved neurological functions of sepsis mice by reliving neuroinflammation and oxidative stress. Inhibition of AMPK attenuated the protective effect of AMA on neurons or the mice's brain tissues. In conclusion, AMA protected against sepsis-induced brain injury by modulating the AMPK/SIRT1/NF-κB pathway.

Hydrogen-rich saline alleviates early brain injury through inhibition of necroptosis and neuroinflammation via the ROS/HO-1 signaling pathway after traumatic brain injury

Traumatic brain injury (TBI) has been recognized as a serious public health issue and a key contributor to disability and death, with a huge economic burden worldwide. Hydrogen, which is a slight and specific cytotoxic oxygen radical scavenger, has been demonstrated to ameliorate early brain injury (EBI) through reactive oxygen species (ROS), oxidative stress injury, apoptosis and necroptosis. Necroptosis refers to a type of programmed cell death process that has a vital function in neuronal cell death following TBI. The specific function of necroptosis in hydrogen-mediated neuroprotection after TBI, however, has yet to be determined. The present study aimed to examine the neuroprotective effects and possible molecular basis that underly hydrogen-rich saline in TBI-stimulated EBI by examining neural necroptosis in the C57BL/6 mouse model. The brain water content, neurological score, neuroinflammatory cytokines (NF-κΒ, TNF-α, IL-6 and IL-1β) and ROS were evaluated using flow cytometry. Malondialdehyde, superoxide dismutase (SOD) and glutathione (GSH) levels were evaluated using a biochemical kit. Receptor-interacting protein kinase (RIP)1, RIP3, Nrf2 and Heme oxygenase-1 (HO-1) were evaluated using western blotting. mRNA of Nrf2 and HO-1 were evaluated using quantitative PCR. Neuronal death was evaluated by TUNEL staining. The outcomes illustrated that hydrogen-rich saline treatment considerably enhanced the neurological score, increased neuronal survival, decreased the levels of serum MDA and brain ROS, increased the levels of serum GSH and SOD. In addition the protein expression levels of RIP1 and RIP3 and the cytokines NF-κB, TNF-α, IL-1β and IL-6 were downregulated compared with the TBI group, which demonstrated that hydrogen-rich saline-induced inhibition of necroptosis and neuroinflammation ameliorated neuronal death following TBI. The neuroprotective capacity of hydrogen-rich saline was demonstrated to be partly dependent on the ROS/heme oxygenase-1 signaling pathway. Taken together, the findings of the present study indicated that hydrogen-rich saline enhanced neurological outcomes in mice and minimized neuronal death by inducing protective effects against neural necroptosis as well as neuroinflammation.

Molecular Hydrogen: A Promising Adjunctive Strategy for the Treatment of the COVID-19

Coronavirus disease 2019 (COVID-19) is an acute respiratory disease caused by a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has no specific and effective treatment. The pathophysiological process of the COVID-19 is an excessive inflammatory response after an organism infects with a virus. Inflammatory storms play an important role in the development of the COVID-19. A large number of studies have confirmed that hydrogen has a therapeutic effect on many diseases via inhibiting excessive inflammatory cells and factors. Recently, a study led by the Academician Zhong Nanshan in China on the treatment of the patients with the COVID-19 by inhalation of a mixed gas composed of hydrogen and oxygen has attracted widespread international attention and hydrogen therapy has also been included in a new treatment plan for the COVID-19 in China. This study mainly describes the mechanism of occurrence of the COVID-19, summarizes the therapeutic effects and underlying mechanisms of hydrogen on the critical disease, and analyzes the feasibility and potential therapeutic targets of hydrogen for the treatment of the COVID-19.

Hydrogen-rich saline alleviates early brain injury through regulating of ER stress and autophagy after experimental subarachnoid hemorrhage

PURPOSE

Subarachnoid hemorrhage (SAH) is a common complication of cerebral vascular disease. Hydrogen has been reported to alleviate early brain injury (EBI) through oxidative stress injury, reactive oxygen species (ROS), and autophagy. Autophagy is a programmed cell death mechanism that plays a vital role in neuronal cell death after SAH. However, the precise role of autophagy in hydrogen-mediated neuroprotection following SAH has not been confirmed.

METHODS

In the present study, the objective was to investigate the neuroprotective effects and potential molecular mechanisms of hydrogen-rich saline in SAH-induced EBI by regulating neural autophagy in the C57BL/6 mice model. Mortality, neurological score, brain water content, ROS, malondialdehyde (MDA), and neuronal death were evaluated.

RESULTS

The results show that hydrogen-rich saline treatment markedly increased the survival rate and neurological score, increased neuron survival, downregulated the autophagy protein expression of Beclin-1 and LC3, and endoplasmic reticulum (ER) stress. That indicates that hydrogen-rich saline-mediated inhibition of autophagy and ER stress ameliorate neuronal death after SAH. The neuroprotective capacity of hydrogen-rich saline is partly dependent on the ROS/Nrf2/heme oxygenase-1 (HO-1) signaling pathway.

CONCLUSIONS

The results of this study demonstrate that hydrogen-rich saline improves neurological outcomes in mice and reduces neuronal death by protecting against neural autophagy and ER stress.

Protective effects and mechanisms of high-dose vitamin C on sepsis-associated cognitive impairment in rats

Sepsis survivors present long-term cognitive deficits. The present study was to investigate the effect of early administration of high-dose vitamin C on cognitive function in septic rats and explore its possible cerebral protective mechanism. Rat sepsis models were established by cecal ligation and puncture (CLP). Ten days after surgery, the Morris water maze test was performed to evaluate the behavior and cognitive function. Histopathologic changes in the hippocampus were evaluated by nissl staining. The inflammatory cytokines, activities of antioxidant enzymes (superoxide dismutase or SOD) and oxidative products (malondialdehyde or MDA) in the serum and hippocampus were tested 24 h after surgery. The activity of matrix metalloproteinase-9 (MMP-9) and expressions of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1(HO-1) in the hippocampus were measured 24 h after surgery. Compared with the sham group in the Morris water maze test, the escape latency of sepsis rats was significantly (P = 0.001) prolonged in the navigation test, whereas the frequency to cross the platform and the time spent in the target quadrant were significantly (P = 0.003) reduced. High-dose vitamin C significantly decreased the escape latency (P = 0.01), but increased the time spent in the target quadrant (P = 0.04) and the frequency to cross the platform (P = 0.19). In the CLP+ saline group, the pyramidal neurons were reduced and distributed sparsely and disorderly, the levels of inflammatory cytokines of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-10 in the serum and hippocampus were significantly increased (P = 0.000), the blood brain barrier (BBB) permeability in the hippocampus was significantly (P = 0.000) increased, the activities of SOD in the serum and hippocampus were significantly (P = 0.000 and P = 0.03, respectively) diminished while the levels of MDA in the serum and hippocampus were significantly (P = 0.007) increased. High-dose vitamin C mitigated hippocampus histopathologic changes, reduced systemic inflammation and neuroinflammation, attenuated BBB disruption, inhibited oxidative stress in brain tissue, and up-regulated the expression of nuclear and total Nrf2 and HO-1. High-dose vitamin C significantly (P < 0.05) decreased the levels of tumor necrosis factor- (TNF)-α, interleukin-6 (IL-6), MDA in the serum and hippocampus, and the activity of MMP-9 in the hippocampus, but significantly (P < 0.05) increased the levels of SOD, the anti-inflammatory cytokine (IL-10) in the serum and hippocampus, and nuclear and total Nrf2, and HO-1 in the hippocampus. In conclusion, high-dose vitamin C can improve cognition impairment in septic rats, and the possible protective mechanism may be related to inhibition of inflammatory factors, alleviation of oxidative stress, and activation of the Nrf2/HO-1 pathway.

What animal models can tell us about long-term cognitive dysfunction following sepsis: A systematic review

Survivors of sepsis often develop long-term cognitive impairments. This review aimed at exploring the results of the behavioral tools and tests which have been used to evaluate cognitive dysfunction in different animal models of sepsis. Two independent investigators searched for sepsis- and cognition-related keywords. 6323 publications were found, of which 355 were selected based on their title, and 226 of these were chosen based on manuscript review. LPS was used to induce sepsis in 171 studies, while CLP was used in 55 studies. Inhibitory avoidance was the most widely used method for assessing aversive memory, followed by fear conditioning and continuous multi-trial inhibitory avoidance. With regard to non-aversive memory, most studies used the water maze, open-field, object recognition, Y-maze, plus maze, and radial maze tests. Both CLP and LPS models of sepsis were effective in inducing short- and long-term behavioral impairment. Our findings help elucidate the mechanisms involved in the pathophysiology of sepsis-induced cognitive changes, as well as the available methods and tests used to study this in animal models.

Perspective of Molecular Hydrogen in the Treatment of Sepsis

Sepsis is the main cause of death in critically ill patients with no effective treatment. Sepsis is lifethreatening organ dysfunction due to a dysregulated host response to infection. As a novel medical gas, molecular hydrogen (H₂) has a therapeutic effect on many diseases, such as sepsis. H₂ treatment exerts multiple biological effects, which can effectively improve multiple organ injuries caused by sepsis. However, the underlying molecular mechanisms of hydrogen involved in the treatment of sepsis remain elusive, which are likely related to anti-inflammation, anti-oxidation, anti-apoptosis, regulation of autophagy and multiple signaling pathways. This review can help better understand the progress of hydrogen in the treatment of sepsis, and provide a theoretical basis for the clinical application of hydrogen therapy in sepsis in the future.

Hydrogen and therapeutic gases for neonatal hypoxic-ischemic encephalopathy: potential neuroprotective adjuncts in translational research

Numerous studies have examined the potential use of therapeutic gases for the treatment of various neurological disorders. Hydrogen gas, a promising neuroprotective agent, has been a focus of study due to its potent antioxidative properties. In translational research into adult diseases, hydrogen has been shown to be neuroprotective in disorders such as cerebral ischemia and traumatic brain injury, and in neurodegenerative diseases such as Alzheimer's disease. Animal and human studies have verified the safety and feasibility of molecular hydrogen. However, despite extensive research on its efficacy in adults, only a few studies have investigated its application in pediatric and neonatal medicine. Neonatal hypoxic-ischemic encephalopathy (HIE) is characterized by damage to neurons and other cells of the nervous system. One of the major contributing factors is excessive exposure to oxidative stress. Current research interest in HIE is shifting toward new neuroprotective agents, as single agents or as adjuncts to therapeutic hypothermia. Here, we review therapeutic gases, particularly hydrogen, and their potentials and limitations in the treatment of HIE in newborns. IMPACT: Translational animal models of neonatal HIE are a current focus of research into the therapeutic usefulness of various gases. Hydrogen ventilation as a single agent or in combination with therapeutic hypothermia shows short- and long-term neuroprotection in neonatal translational HIE models. The optimal target severity for therapeutic interventions should be well established to improve outcomes.

Reducing LncRNA-5657 expression inhibits the brain inflammatory reaction in septic rats

Our preliminary study found that the long noncoding RNA (LncRNA)-5657 can reduce the expression of inflammatory factors during inflammatory reactions in rat glial cells. However, the role played by LncRNA-5657 during septic brain injury remains unclear. In the present study, rat models of septic encephalopathy were established by cecal ligation and puncture, and then the rats were treated with a hippocampal injection small hairpin RNA (shRNA) against LncRNA-5657 (sh-LnCRNA-5657). The sh-LncRNA-5657 treatment reduced the level of neuronal degeneration and necrosis in the rat hippocampus, reduced the immunoreactivities of aquaporin 4, heparanase, and metallopeptidase-9, and lowered the level of tumor necrosis factor-alpha. Glial cells were pre-treated with sh-LncRNA-5657 and then treated with 1 µg/mL lipopolysaccharide. Sh-LncRNA-5657 transfection decreased the expression of LncRNA-5657 in lipopolysaccharide-treated glial cells and decreased the mRNA and protein levels of tumor necrosis factor-alpha, interleukin-1β, and interleukin-6. These findings suggested that LncRNA-5657 expression can significantly reduce the inflammatory reaction during septic encephalopathy and induce protective effects against this disease. This study was approved by the Institutional Ethics Committee at the First Affiliated Hospital of Nanchang University of China (approval No. 2017-004) in 2017.

Isoflurane reduces septic neuron injury by HO‑1‑mediated abatement of inflammation and apoptosis

Sepsis-associated encephalopathy (SAE) frequently occurs in critically ill patients with severe systemic infections. Subanesthetic isoflurane (0.7% ISO) possesses anti-inflammatory, antioxidant and anti-apoptotic properties against a number of human diseases, including brain injury. The activation of heme oxygenase-1 (HO-1) impedes inflammation, oxidation and apoptosis, thus alleviating sepsis-induced brain damage. However, whether 0.7% ISO affords protection against septic neuronal injury involving HO-1 activation is unclear. The present study aimed to investigate the neuroprotective effects of 0.7% ISO and its potential underlying mechanisms in SAE using a mouse model established by cecal ligation and puncture (CLP). The results indicated that the expression and activity of HO-1 in the mouse hippocampus were increased by CLP, and further enhanced by ISO. ISO reduced the death rate, brain water content and blood-brain barrier disruption, but improved the learning and memory functions of CLP-treated mice. ISO significantly decreased the production of pro-inflammatory cytokines and the levels of oxidative indictors in the serum and hippocampus, as well as the number of apoptotic neurons and the expression of pro-apoptotic proteins in the hippocampus. Inversely, anti-inflammatory factors, antioxidative enzymes and anti-apoptotic proteins were markedly increased by ISO administration. However, the neuroprotective effects of ISO were abolished by a HO-1 inhibitor. Overall, these findings suggested that 0.7% ISO alleviated SAE via its anti-inflammatory, antioxidative and anti-apoptotic properties, which involved the activated form of HO-1.

Molecular and Cellular Mechanisms Associated with Effects of Molecular Hydrogen in Cardiovascular and Central Nervous Systems

The increased production of reactive oxygen species and oxidative stress are important factors contributing to the development of diseases of the cardiovascular and central nervous systems. Molecular hydrogen is recognized as an emerging therapeutic, and its positive effects in the treatment of pathologies have been documented in both experimental and clinical studies. The therapeutic potential of hydrogen is attributed to several major molecular mechanisms. This review focuses on the effects of hydrogen on the cardiovascular and central nervous systems, and summarizes current knowledge about its actions, including the regulation of redox and intracellular signaling, alterations in gene expressions, and modulation of cellular responses (e.g., autophagy, apoptosis, and tissue remodeling). We summarize the functions of hydrogen as a regulator of nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated redox signaling and the association of hydrogen with mitochondria as an important target of its therapeutic action. The antioxidant functions of hydrogen are closely associated with protein kinase signaling pathways, and we discuss possible roles of the phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) and Wnt/β-catenin pathways, which are mediated through glycogen synthase kinase 3β and its involvement in the regulation of cellular apoptosis. Additionally, current knowledge about the role of molecular hydrogen in the modulation of autophagy and matrix metalloproteinases-mediated tissue remodeling, which are other responses to cellular stress, is summarized in this review.

Molecular hydrogen alleviates brain injury and cognitive impairment in a chronic sequelae model of murine polymicrobial sepsis

Sepsis-related encephalopathy (SAE), which causes a series of brain injuries and long-term, potentially irreversible cognitive dysfunction, is closely associated with increased morbidity and mortality. Hydrogen (H2) is a new type of medical gas molecule that has been widely used in the treatment of various diseases in recent years. The aim of the present study was to explore the protective effects of H2 inhalation on brain injury and long-term cognitive impairment in an improved chronic septic mouse model. Male C57BL/6J mice were randomized into four groups: Control, Control + H2, SAE and SAE + H2. The SAE and Control models were established by intraperitoneal injection of human stool suspension or saline in mice. H2 (2%) was inhaled for 60 min at 1 h and 6 h after SAE or Control treatment. The survival rates were recorded for 14 days (days 1-14) and the Morris Water Maze was performed for 7 days (days 8-14). To assess the severity of the brain injury, hematoxylin and eosin staining, Nissl staining, Evans blue (EB) extravasation and the wet/dry weight ratio of brain tissue were detected 24 h after SAE or Control treatment. In addition, inflammatory cytokines, such as tumor necrosis factor (TNF)-α, interleukin 6 (IL-6), high-mobility group box 1 (HMGB1), as well as the protein levels of nuclear factor-erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), zonula occludens-1 (ZO-1) and Occludin, were measured 6, 12 and 24 h after SAE or Control treatment. The results showed that H2 treatment increased survival rates, mitigated cognitive impairment, reduced hippocampal histological damage, decreased EB and water content, and decreased the levels of TNF-α, IL-6, HMGB1, Nrf2, HO-1, ZO-1 and Occludin, as compared with the SAE group. These data revealed that 2% H2 could suppress brain damage and improve cognitive function in septic mice by inhibiting oxidative stress, inflammatory response and the sepsis-induced blood-brain barrier (BBB) disruption.

iTRAQ-Based Quantitative Proteomic Analysis of Intestines in Murine Polymicrobial Sepsis with Hydrogen Gas Treatment

Objective

Sepsis-associated intestinal injury has a higher morbidity and mortality in patients with sepsis, but there is still no effective treatment. Our research team has proven that inhaling 2% hydrogen gas (H₂) can effectively improve sepsis and related organ damage, but the specific molecular mechanism of its role is not clear. In this study, isobaric tags for relative and absolute quantitation (iTRAQ)-based quantitative proteomics analysis was used for studying the effect of H₂ on intestinal injury in sepsis.

Methods

Male C57BL/6J mice were used to prepare a sepsis model by cecal ligation and puncture (CLP). The 7-day survival rates of mice were measured. 4-kd fluorescein isothiocyanate-conjugated Dextran (FITC-dextran) blood concentration measurement, combined with hematoxylin-eosinstain (HE) staining and Western blotting, was used to study the effect of H₂ on sepsis-related intestinal damage. iTRAQ-based liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis was used for studying the proteomics associated with H₂ for the treatment of intestinal injury.

Results

H₂ can significantly improve the 7-day survival rates of sepsis mice. The load of blood and peritoneal lavage bacteria was increased, and H₂ treatment can significantly reduce it. CLP mice had significant intestinal damage, and inhalation of 2% hydrogen could significantly reduce this damage. All 4194 proteins were quantified, of which 199 differentially expressed proteins were associated with the positive effect of H₂ on sepsis. Functional enrichment analysis indicated that H₂ may reduce intestinal injury in septic mice through the effects of thyroid hormone synthesis and nitrogen metabolism signaling pathway. Western blot showed that H₂ was reduced by down-regulating the expressions of deleted in malignant brain tumors 1 protein (DMBT1), insulin receptor substrate 2 (IRS2), N-myc downregulated gene 1 (NDRG1) and serum amyloid A-1 protein (SAA1) intestinal damage in sepsis mice.

Conclusion

A total of 199 differential proteins were related with H₂ in the intestinal protection of sepsis. H₂-related differential proteins were notably enriched in the following signaling pathways, including thyroid hormone synthesis signaling pathway, nitrogen metabolism signaling pathways, digestion and absorption signaling pathways (vitamins, proteins and fats). H₂ reduced intestinal injury in septic mice by down-regulating the expressions of SAA1, NDRG1, DMBT1 and IRS2.

Isoorientin Inhibits Inflammation in Macrophages and Endotoxemia Mice by Regulating Glycogen Synthase Kinase 3β

Isoorientin has anti-inflammatory effects; however, the mechanism remains unclear. We previously found isoorientin is an inhibitor of glycogen synthase kinase 3β (GSK3β) in vitro. Overactivation of GSK3β is associated with inflammatory responses. GSK3β is inactivated by phosphorylation at Ser9 (i.e., p-GSK3β). Lithium chloride (LiCl) inhibits GSK3β and also increases p-GSK3β (Ser9). The present study investigated the anti-inflammatory effect and mechanism of isoorientin via GSK3β regulation in lipopolysaccharide- (LPS-) induced RAW264.7 murine macrophage-like cells and endotoxemia mice. LiCl was used as a control. While AKT phosphorylates GSK3β, MK-2206, a selective AKT inhibitor, was used to activate GSK3β via AKT inhibition (i.e., not phosphorylate GSK3β at Ser9). The proinflammatory cytokines TNF-α, IL-6, and IL-1β were detected by ELISA or quantitative real-time PCR, while COX-2 by Western blotting. The p-GSK3β and GSK3β downstream signal molecules, including NF-κB, ERK, Nrf2, and HO-1, as well as the tight junction proteins ZO-1 and occludin were measured by Western blotting. The results showed that isoorientin decreased the production of TNF-α, IL-6, and IL-1β and increased the expression of p-GSK3β in vitro and in vivo, similar to LiCl. Coadministration of isoorientin and LiCl showed antagonistic effects. Isoorientin decreased the expression of COX-2, inhibited the activation of ERK and NF-κB, and increased the activation of Nrf2/HO-1 in LPS-induced RAW264.7 cells. Isoorientin increased the expressions of occludin and ZO-1 in the brain of endotoxemia mice. In summary, isoorientin can inhibit GSK3β by increasing p-GSK3β and regulate the downstream signal molecules to inhibit inflammation and protect the integrity of the blood-brain barrier and the homeostasis in the brain.

Ultra high-sensitive, prompt response and recovering Pt/(Pt+SiO 2) cermet layer/GaN-based hydrogen sensor for life-saving applications

In this work, we report an ultra-high sensitive (S = 1.4 × 108%), prompt response and recovering Pt/Pt+SiO2 cermet layer/GaN-based hydrogen (H2) sensor. A sensor fabricated with a 15 nm cermet layer, comprising Pt and SiO2, deposited between 15 nm Pt and GaN layers, exhibits significantly enhanced sensitivity in the detection of 4 %H2 by ≈ 300×, as compared to the reference Pt/GaN sensor at ambient temperature (300 K). Furthermore, the sensitivity of the our sensor shows very weak dependence on temperature (T) with maximum sensitivity ([Formula: see text]) reducing from 1.4 × 108% to 2.3 × 107% as temperature increases from 300 to 423 K. The shift in the threshold voltage of the test sensor (ΔV t,test = 767 mV) increases by 50 % as compared to the shift in threshold voltage of the control sensor (ΔV t,control = 511 mV) at 1 mA/cm2. In addition, the cermet sensor also demonstrates fast response/recovery time, which reduces from 4.58 (2.36) seconds to 94 (39) milliseconds as the temperature increases from 300 to 423 K. The maximum sensitivity ([Formula: see text]), response (τ a ) and recovery (τ b ) times of the test sensor when exposed to 10 000 ppm of H2 are 3.9 × 107%, 30 secs and 30.1 secs respectively. The shift in the threshold voltage of the test sensor at 1 mA/cm2 when exposed to 100 ppm, 1000 ppm, 5000 ppm, and 10 000 ppm are 40 mV, 70 mV, 460 mV, and 600 mV, respectively. The 2-Dimensional (2D) trapping of H-atoms by the oxygen atoms present in the Pt+SiO2 cermet layer and porous/compact layer models explains the underlying mechanism, which results in a significant improvement of the sensing characteristics of the test sensor. The Thermionic Emission (TE) model effectively models the current density (J) - voltage (V) characteristics of both control and test sensors, with and without hydrogen. The prompt detection of high percentages of hydrogen in life-saving and commercial fuel applications becomes possible with the Pt+SiO2 cermet-based sensor, with its response and recovery times in the order of milliseconds for a temperature range of 363-423 K.

Prospects of molecular hydrogen in perioperative neuroprotection from basic research to clinical application

PURPOSE OF REVIEW

The current systematic review summarizes recent, basic clinical achievements regarding the neuroprotective effects of molecular hydrogen in distinct central nervous system conditions.

RECENT FINDINGS

Perioperative neuroprotection remains a major topic of clinical anesthesia. Various gaseous molecules have previously been explored as a feasible therapeutic option in neurological disorders. Among them, molecular hydrogen, which has emerged as a novel and potential therapy for perioperative neuroprotection, has received much attention.

SUMMARY

Fundamental and clinical evidence supports the antioxidant, antiinflammation, antiapoptosis and mitochondrial protective effects of hydrogen in the pathophysiology of nervous system diseases. The clinically preventive and therapeutic effects of hydrogen on different neural diseases, however, remain uncertain, and the lack of support by large randomized controlled trials has delayed its clinical application.

Molecular hydrogen: A potential radioprotective agent

In recent years, many studies have shown that hydrogen has therapeutic and preventive effects on various diseases. Its selective antioxidant properties were well noticed. Most of the ionizing radiation-induced damage is caused by hydroxyl radicals (OH) from radiolysis of H₂O. Since hydrogen can mitigate such damage through multiple mechanisms, it presents noteworthy potential as a novel radio-protective agent. This review analyses possible mechanisms for hydrogen's radioprotective properties and effective delivery methods. We also look into details of vitro and vivo studies for hydrogen's radioprotective effects, and clinical practices. We conclude that hydrogen has good potential in radio-protection, with evidence that warrants greater research efforts in this field.

Chronic molecular hydrogen inhalation mitigates short and long-term memory loss in polymicrobial sepsis

The central nervous system (CNS) is one of the first physiological systems to be affected in sepsis. During the exacerbated systemic inflammatory response at the early stage of sepsis, circulatory inflammatory mediators are able to reach the CNS leading to neuroinflammation and, consequently, long-term impairment in learning and memory formation is observed. The acute treatment with molecular hydrogen (H₂) exerts important antioxidative, antiapoptotic, and anti-inflammatory effects in sepsis, but little is known about the mechanism itself and the efficacy of chronic H₂ inhalation in sepsis treatment. Thus, we tested two hypotheses. We first hypothesized that chronic H₂ inhalation is also an effective therapy to treat memory impairment induced by sepsis. The second hypothesis is that H₂ treatment decreases sepsis-induced neuroinflammation in the hippocampus and prefrontal cortex, important areas related to short and long-term memory processing. Our results indicate that (1) chronic exposure of hydrogen gas is a simple, safe and promising therapeutic strategy to prevent memory loss in patients with sepsis and (2) acute H₂ inhalation decreases neuroinflammation in memory-related areas and increases total nuclear factor E2-related factor 2 (Nrf2), a transcription factorthat regulates a vast group of antioxidant and inflammatory agents expression in these areas of septic animals.

iTRAQ-based quantitative proteomic analysis of the therapeutic effects of 2% hydrogen gas inhalation on brain injury in septic mice

Sepsis encephalopathy (SAE) has a high incidence and mortality rate in patients with sepsis; however, there is currently no effective treatment. Our previous studies have reported that 2% hydrogen (H₂) gas inhalation had a protective effect on sepsis and SAE; however, the specific mechanism have not been fully elucidated. In the current study, male Institute of Cancer Research mice were either used to create the cecal ligation and puncture (CLP) model or for sham surgery, followed by 2% H₂ gas inhalation for 60 min beginning at 1 and 6 h following sham or CLP surgeries. The isobaric tags for relative and absolute quantitation (iTRAQ)-based quantitative proteomics combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis, hematoxylin and eosin (H&E) staining, Nissl staining, and western blot analysis were used to investigate the effects of H₂ on brain injury in mice with sepsis. The results of the H&E, and Nissl staining indicated that the CLP mice had a significant brain injury, which was characterized by aggravated pathological damage and was alleviated by 2% H₂ inhalation. Quantitative proteomics based on iTRAQ combined with LC-MS/MS analysis quantified a total of 5317 proteins, of which 39 were connected with the protective mechanism of H₂. In addition, H₂ could regulate the immune and the coagulation systems. Furthermore, western blot analysis revealed that H₂ decreased SAE in septic mice by downregulating the protein expression levels of SMAD4, DPYS, PTGDS and upregulating the expression level of CUL4A. These results provide insights into the mechanism of the positive effect of H₂ on SAE and contribute to the clinical application of H₂ in patients with sepsis.

Hydrogen Gas Alleviates Sepsis-Induced Brain Injury by Improving Mitochondrial Biogenesis Through the Activation of PGC-α in Mice

ABSTRACT

Sepsis-associated encephalopathy (SAE) affects approximately one-third of septic patients, and there is a lack of effective therapeutics for SAE. Hydrogen gas is a new medical gas that exerts anti-inflammation, antioxidation, and anti-apoptotic effects and can effectively protect septic mice. Mitochondrial dysfunction, which can be improved by mitochondrial biogenesis, is a type of molecular pathology in sepsis. Peroxisome proliferator-activated receptor gamma co-activator 1α (PGC-1α), which can be inhibited by SR-18292, is the key regulatory factor of mitochondrial biogenesis. Therefore, we investigated the effects of hydrogen gas on mitochondrial function and mitochondrial biogenesis in mice with SAE and the related regulatory mechanisms. Cecal ligation and puncture was used to induce sepsis in mice. The mice with hydrogen gas therapy were exposed to 2% H2 inhalation for 1 h beginning at both 1 and 6 h after operation, and mice were also injected with a PGC-1α inhibitor, SR-18292. We recorded the 7-day survival rates of the mice and detected their cognitive function using a Y-maze test. The Nissl bodies in the CA1 region of hippocampus were observed by Nissl staining, and the apoptotic cells were observed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay staining. The mitochondrial membrane potential (MMP), adenosine triphosphate (ATP) level, and mitochondrial respiratory chain complexes I and II were analyzed using commercial kits. The mitochondrial morphology was observed by transmission electron microscopy. The expression levels of PGC-1α, nuclear respiratory factor 2 (NRF2), and mitochondrial transcription factor A (Tfam) were detected by Western blot analysis. The present study showed that hydrogen gas therapy increased the 7-day survival rate, improved cognitive function, increased the mitochondrial function (MMP, ATP level, complex I activity) and expression of mitochondrial biogenesis parameters (PGC-1α, NRF2, Tfam). However, the injection of SR-18292 (a PGC-1α inhibitor) decreased mitochondrial function, PGC-1α activation, and expression of NRF2 and Tfam. Therefore, these results indicate that hydrogen gas alleviates sepsis-induced brain injury in mice by improving mitochondrial biogenesis through the activation of PGC-1α.

Hydrogen gas therapy improves survival rate and neurological deficits in subarachnoid hemorrhage rats: a pilot study

The high morbidity, high mortality, and significant shortage of effective therapies for subarachnoid hemorrhage (SAH) have created an urgency to discover novel therapies. Human studies in Asia have established the safety of hydrogen gas in the treatment of hepatic, renal, pulmonary, and cardiac diseases. Mechanistically, hydrogen gas has been shown to affect oxidative stress, inflammation, and apoptosis. We hypothesized that hydrogen therapy would improve neurological function and increase survival rate in SAH. High dose hydrogen gas (66% at 3 L/min) was administered for 2 hours at 0.5, 8, and 18 hours after SAH. This treatment increased 72-hour survival rate and provided 24-hour neuroprotection after SAH in rats. To our knowledge, this is the first report demonstrating that high dose hydrogen gas therapy reduces mortality and improves outcome after SAH. Our results correlate well with the proposed mechanisms of hydrogen gas therapy within the literature. We outline four pathways and downstream targets of hydrogen gas potentially responsible for our results. A potentially complex network of pathways responsible for the efficacy of hydrogen gas therapy, along with a limited mechanistic understanding of these pathways, justifies further investigation to provide a basis for clinical trials and the advancement of hydrogen gas therapy in humans. This study was approved by the Institutional Animal Care and Use Committee of Loma Linda University, USA (Approval No. 8160016) in May 2016.

Hydrogen attenuates sepsis-associated encephalopathy by NRF2 mediated NLRP3 pathway inactivation

OBJECTIVE

Sepsis-associated encephalopathy (SAE) is a major cause of mortality worldwide. Oxidative stress, inflammatory response and apoptosis participate in the pathogenesis of SAE. Nuclear factor erythroid 2-related factor 2 (Nrf2) and nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) pathway is involved in oxidative stress and inflammatory response. We reported that hydrogen gas protected against sepsis in wild-type (WT) but not Nrf2 knockout (KO) mice. Therefore, it is vital to identify the underlying cause of hydrogen gas treatment of sepsis-associated encephalopathy.

METHODS

SAE was induced in WT and Nrf2 KO mice by cecal ligation and puncture (CLP). As a NLRP3 inflammasome inhibitor, MCC950 (50 mg/kg) was administered by intraperitoneal (i.p.) injection before operation. Hydrogen gas (H₂)-rich saline solution (5 mL/kg) was administered by i.p. injection at 1 h and 6 h after sham and CLP operations. Brain tissue was collected to assess the NLRP3 and Nrf2 pathways by western blotting, reverse transcription-polymerase chain reaction (RT-PCR) and immunofluorescence.

RESULTS

SAE increased NLRP3 and Nrf2 expression in microglia. MCC950 inhibited SAE-induced NLRP3 expression, interleukin (IL)-1β and IL-18 cytokine release, neuronal apoptosis and mitochondrial dysfunction. SAE increased NLRP3 and caspase-1 expression in WT mice compared to Nrf2 KO mice. Hydrogen increased Nrf2 expression and inhibited the SAE-induced expression of NLRP3, caspase-1, cytokines IL-1β and IL-18, neuronal apoptosis, and mitochondrial dysfunction in WT mice but not Nrf2 KO mice.

CONCLUSION

SAE increased NLRP3 and Nrf2 expression in microglia. Hydrogen alleviated inflammation, neuronal apoptosis and mitochondrial dysfunction via inhibiting Nrf2-mediated NLRP3 pathway.

Hydrogen exerts neuroprotection by activation of the miR-21/PI3K/AKT/GSK-3β pathway in an in vitro model of traumatic brain injury

Few studies have explored the effect of hydrogen on neuronal apoptosis or impaired nerve regeneration after traumatic brain injury, and the mechanisms involved in these processes are unclear. In this study, we explored neuroprotection of hydrogen‐rich medium through activation of the miR‐21/PI3K/AKT/GSK‐3β pathway in an in vitro model of traumatic brain injury. Such model adopted PC12 cells with manual scratching. Then, injured cells were cultured in hydrogen‐rich medium for 48 hours. Expression of miR‐21, p‐PI3K, p‐Akt, p‐GSK‐3β, Bax and Bcl‐2 was measured using RT‐qPCR, Western blot analysis and immunofluorescence staining. Rate of apoptosis was determined using TUNEL staining. Neuronal regeneration was assessed using immunofluorescence staining. The results showed that hydrogen‐rich medium improved neurite regeneration and inhibited apoptosis in the injured cells. Scratch injury was accompanied by up‐regulation of miR‐21, p‐PI3K, p‐Akt and p‐GSK‐3β. A miR‐21 antagomir inhibited the expression of these four molecules, while a PI3K blocker only affected the three proteins and not miR‐21. Both the miR‐21 antagomir and PI3K blocker reversed the protective effect of hydrogen. In conclusion, hydrogen exerted a neuroprotective effect against neuronal apoptosis and impaired nerve regeneration through activation of miR‐21/PI3K/AKT/GSK‐3β signalling in this in vitro model of traumatic brain injury.

Molecular hydrogen: current knowledge on mechanism in alleviating free radical damage and diseases

Ever since molecular hydrogen was first reported as a hydroxyl radical scavenger in 2007, the beneficial effect of hydrogen was documented in more than 170 disease models and human diseases including ischemia/reperfusion injury, metabolic syndrome, inflammation, and cancer. All these pathological damages are concomitant with overproduction of reactive oxygen species (ROS) where molecular hydrogen has been widely demonstrated as a selective antioxidant. Although it is difficult to construe the molecular mechanism of hydrogen's biomedical effect, an increasing number of studies have been helping us draw the picture clearer with days passing by. In this review, we summarized the current knowledge on systemic and cellular modulation by hydrogen treatment. We discussed the antioxidative, anti-inflammatory, and anti-apoptosis effects of hydrogen, as well as its protection on mitochondria and the endoplasmic reticulum, regulation of intracellular signaling pathways, and balancing of the immune cell subtypes. We hope that this review will provide organized information that prompts further investigation for in-depth studies of hydrogen effect.

Hydrogen treatment prevents lipopolysaccharide-induced pulmonary endothelial cell dysfunction through RhoA inhibition

BACKGROUND

Pulmonary microvascular endothelial cells (PMVECs) are initial targets of sepsis-induced acute lung injury (ALI). During the apoptosis of PMVECs, tight junctions (TJ) and adherens junctions (AJ) are firstly damaged. Previous studies have suggested hydrogen treatment can protect lung microvasculature of mice from sepsis-induced endothelial dysfunction and maintain the coherence of pulmonary endothelium, but the underlying mechanism remains unclear.

METHODS

We investigated the role of hydrogen-rich medium on regulating intercellular junction proteins under lipopolysaccharide (LPS) treatment which mimicked sepsis in vitro. Changes of cytoskeleton regulatory protein ROCK and RhoA as well as PMVEC apoptotic rate were examined.

RESULTS

LPS treatment reduced the expression levels of occludin and VE-cadherin in PMVECs, while hydrogen-rich medium can recover these changes. Furthermore, H₂ can significantly ameliorate the excessive expression of ROCK and RhoA under sepsis-mimicking condition. The application of RhoA activator U-46619 resulted in a more significant elevation in cell apoptotic rate as well as reduction in the expression of junctional proteins. Using H₂ can almost completely inhibit the effects of RhoA activator.

CONCLUSIONS

Our findings suggest that RhoA is a crucial protein in the signaling pathway of LPS-induced endothelial cell dysfunction. Hydrogen treatment can prevent LPS-induced junctional injury and cell death by inhibiting the activity of RhoA.