Hydrogen-induced Neuroprotection in Neonatal Hypoxic-ischemic Encephalopathy

Hydrogen inhalation therapy regulates lactic acid metabolism following subarachnoid hemorrhage through the HIF-1α pathway

The neuroprotective effects of hydrogen have been demonstrated, but the mechanism is still poorly understood. In a clinical trial of inhaled hydrogen in patients with subarachnoid hemorrhage (SAH), we found that hydrogen reduced the accumulation of lactic acid in the nervous system. There are no studies demonstrating the regulatory effect of hydrogen on lactate and in this study we hope to further clarify the mechanism by which hydrogen regulates lactate metabolism. In cell experiments, PCR and Western Blot showed that HIF-1α was the target related to lactic acid metabolism that changed the most before and after hydrogen intervention. HIF-1α levels were suppressed by hydrogen intervention treatment. Activation of HIF-1α inhibited the lactic acid-lowering effect of hydrogen. We have also demonstrated the lactic acid-lowering effect of hydrogen in animal studies. Our work clarifies that hydrogen can regulate lactate metabolism via the HIF-1αpathway, providing new insights into the neuroprotective mechanisms of hydrogen.

Hydrogen-Rich Saline-A Novel Neuroprotective Agent in a Mouse Model of Experimental Cerebral Ischemia via the ROS-NLRP3 Inflammasome Signaling Pathway In Vivo and In Vitro

BACKGROUND

Our previous research revealed that inflammation plays an important role in the pathophysiology of cerebral ischemia. The function of the NOD-like receptor protein 3 (NLRP3) inflammasome is to activate the inflammatory process. Recent findings suggest that reactive oxygen species (ROS) are essential secondary messengers that activate the NLRP3 inflammasome. Hydrogen-rich saline (HS) has attracted attention for its anti-inflammatory properties. However, the protective effect and possible mechanism of HSin brain ischemia have not been well elucidated.

METHODS

To test the therapeutic effect of HS, we established a mouse model of distal middle cerebral artery occlusion (dMCAO) and an in vitro model of BV2 cells induced by lipopolysaccharide (LPS). The ROS scavenger N-acetylcysteine (NAC) was used to investigate the underlying mechanisms of HS.

RESULTS

HS significantly improved neurological function, reduced infarct volume, and increased cerebral blood flow in a dMCAO mouse model. ROS, NLRP3, Caspase-1, and IL-1β expression increased after cerebral ischemia, and this was reversed by HS treatment. In BV2 cells, the application of NAC further demonstrated that HS could effectively inhibit the expression of the ROS-activated NLRP3 inflammasome.

CONCLUSIONS

HS, as a novel therapeutic option, could exert protect the brain by inhibiting the activation of the ROS-NLRP3 signaling pathway after cerebral ischemia.

miR-204-5p Inhibits the Proliferation and Differentiation of Fetal Neural Stem Cells by Targeting Wingless-Related MMTV Integration Site 2 to Regulate the Ephrin-A2/EphA7 Pathway

Neonatal hypoxic ischemic encephalopathy (HIE) is mainly resulted from perinatal asphyxia, which can be repaired by NSCs. miR-204-5p is claimed to impact the activity NSCs. Our research will probe the miR-204-5p function in oxygen-glucose deprivation (OGD)-treated NSCs. miR-204-5p level was enhanced and WNT2 level was reduced in HIE rats. Rat NSCs were stimulated with OGD condition under the managing of mimic or inhibitor of miR-204-5p. The declined cell viability, enhanced apoptosis, downregulated Tuj1 and GFAP levels, and shortened total neurite length were observed in OGD-treated NSCs, which were further aggravated by the mimic and rescued by the inhibitor of miR-204-5p. Furthermore, the inactivated WNT2 and Ephrin-A2/EphA7 signaling pathway in OGD-stimulated NSCs was further repressed by the mimic and rescued by the inhibitor of miR-204-5p. In addition, WNT2 was confirmed as the targeting of miR-204-5p. Lastly, the function of miR-204-5p mimic on the proliferation, apoptosis, differentiation, WNT2 and Ephrin-A2/EphA7 signaling pathway in OGD-stimulated NSCs was abolished by HLY78, an activator of Wnt signaling. Collectively, miR-204-5p repressed the growth and differentiation of fetal NSCs by targeting WNT2 to regulate the Ephrin-A2/EphA7 pathway.

The protective effect of MiR-27a on the neonatal hypoxic-ischemic encephalopathy by targeting FOXO1 in rats

BACKGROUND

Neonatal hypoxic-ischemic encephalopathy (HIE), a kind of hypoxic-ischemic brain damage caused by perinatal asphyxia, is the most crucial cause of neonatal death and long-term neurological dysfunction in children. We aimed to investigate the protective effects of micro (mi)R-27a on HIE in neonatal rats.

METHODS

A rat model of neonatal HIE was constructed by modification of the Rice-Vannucci model. Real-time quantitative polymerase chain reaction (RT-qPCR) was used to test the expressions of miR-27a, FOXO1 messenger RNA (mRNA), interleukin-1β (IL-1β) mRNA, and tumor necrosis factor-α (TNF-α) mRNA, and western blot was applied to test the expression of FOXO1. In order to overexpress miR-27a, an intracerebroventricular injection (i.c.v) of miR-27a mimic was administered. We adopted 2,3,5-triphenytetrazolium chloride (TTC) staining and brain water content measurement to test the effects of miR-27a on the infarcted volume and edema in brain after HIE. Flow cytometry (FCM) analysis was applied to test the effects of miR-27a on the infiltrated peripheral immune cells in the rat brains after HIE.

RESULTS

We successfully established a rat model of neonatal HIE. It was revealed that the expressions of miR-27a decreased gradually after HIE, however, the expressions of FOXO1 mRNA increased. After injection of the miR-27a mimic, the expression of miR-27a in the rat HIE model brains was significantly upregulated, however, the expression of FOXO1 was robustly downregulated. Both TTC staining and brain water content showed that the infarcted volume and brain edema was markedly increased after HIE. Interestingly, the overexpression of miR-27a reduced the infarcted volume and edema induced by HIE. Additionally, RT-qPCR and FCM analysis showed that HIE lead to increases of IL-1β, TNF-α, and infiltrated immune cells. Overexpression of miR-27a could reduce the expressions of IL-1β mRNA and TNF-α mRNA, and the cell numbers of infiltrated peripheral macrophages and neutrophils in the brain.

CONCLUSIONS

MiR-27a plays protective roles by reducing infarct volume and brain edema, and inhibiting inflammatory factors and infiltrated peripheral immune cells by targeting FOXO1 in neonatal HIE rats.

Hydrogen Attenuated Inflammation Response and Oxidative in Hypoxic Ischemic Encephalopathy via Nrf2 Mediated the Inhibition of NLRP3 and NF-κB

Hypoxia and ischemia cause neonatal encephalopathy and brain injury and can further result in cerebral palsy, cognitive impairment, growth restriction, and epilepsy. Induction of neuroprotection is a crucial therapeutic strategy for the treatment of perinatal hypoxic-ischaemic encephalopathy (HIE). Hydrogen has neuroprotective effects against brain-related diseases. Inflammation and oxidative stress are the two main pathophysiological mechanisms in neonatal hypoxic-ischaemic injury. Nuclear factor erythroid 2-related factor 2 (Nrf2) is an endogenous redox-sensitive transcription factor that participates in the antioxidant defence system through its effects on inflammation and oxidative stress. Herein, the research focuses on the mechanisms by which Nrf2 participates in the protection of hydrogen against HIE. The model of HIE was established by ligation of the right carotid artery and hypoxia in wild-type (WT) and Nrf2-/- mice. First, Nrf2 pathway activity was detected after hypoxia-ischaemia (HI) followed or not by hydrogen treatment. Brain injury, apoptosis, the inflammatory response, oxidative stress injury, and learning and memory function were assayed. We found that HI induced Nrf2 expression and signalling activation. Hydrogen alleviated the infarction volume, brain water content, neurological scores, apoptosis and long-term learning and memory functions after HI in WT mice but not in Nrf2-/- mice. Moreover, the oxidative products reactive oxygen species (ROS) and malondialdehyde (MDA) and the cytokines tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6) and High mobility group box 1 (HMGB1) were reduced and the antioxidant enzymes Superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) were upregulated by hydrogen treatment after HI in WT mice, but not in Nrf2-/- mice. In addition, the absence of Nrf2 abolished the suppressive effect of hydrogen on the expression of Nacht, Lrr, and Pyd domains-containing protein 3 (NLRP3) pathway members and p65 NF-κB after HI. Taken together, our findings showed that hydrogen alleviated cellular injury and apoptosis, neurobehavioural deficits, the inflammatory response and oxidative stress via the Nrf2-mediated NLRP3 and NF-κB pathways.

Current Therapies for Neonatal Hypoxic-Ischaemic and Infection-Sensitised Hypoxic-Ischaemic Brain Damage

Neonatal hypoxic-ischaemic brain damage is a leading cause of child mortality and morbidity, including cerebral palsy, epilepsy, and cognitive disabilities. The majority of neonatal hypoxic-ischaemic cases arise as a result of impaired cerebral perfusion to the foetus attributed to uterine, placental, or umbilical cord compromise prior to or during delivery. Bacterial infection is a factor contributing to the damage and is recorded in more than half of preterm births. Exposure to infection exacerbates neuronal hypoxic-ischaemic damage thus leading to a phenomenon called infection-sensitised hypoxic-ischaemic brain injury. Models of neonatal hypoxia-ischaemia (HI) have been developed in different animals. Both human and animal studies show that the developmental stage and the severity of the HI insult affect the selective regional vulnerability of the brain to damage, as well as the subsequent clinical manifestations. Therapeutic hypothermia (TH) is the only clinically approved treatment for neonatal HI. However, the number of HI infants needed to treat with TH for one to be saved from death or disability at age of 18-22 months, is approximately 6-7, which highlights the need for additional or alternative treatments to replace TH or increase its efficiency. In this review we discuss the mechanisms of HI injury to the immature brain and the new experimental treatments studied for neonatal HI and infection-sensitised neonatal HI.