Hydrogen Gas Protects Brain from Injury by Reducing Inflammation in Rats

Authors
Journal
Chinese Critical Care Medicine
Year
DOI
10.3760/cma.j.cn121430-20220712-00656
Study Type
Rat
Outcome
Positive
Peer Reviewed
Yes
Country
China
Health Condition
Traumatic Brain Injury
Body System
Nervous System

TL;DR

Breathing hydrogen gas helps reduce brain damage and inflammation in rats after a traumatic brain injury.

Key Finding

Hydrogen gas inhalation reduced brain swelling, inflammation, and neuronal cell death in rats with traumatic brain injury by suppressing NLRP3 inflammasome activation in the brain cortex.

Summary

Researchers gave rats with traumatic brain injuries (TBI) hydrogen gas to breathe and measured how it affected inflammation and cell death in the brain. They found that hydrogen gas reduced brain swelling, decreased the activation of inflammatory proteins (NLRP3 inflammasomes), lowered levels of inflammatory chemicals, and reduced the death of brain cells. The protective effects were similar to using a drug that blocks NLRP3, and combining hydrogen gas with that drug provided even greater benefits.

Practical Takeaway

This rat study suggests hydrogen gas may have neuroprotective properties for traumatic brain injury through anti-inflammatory mechanisms, but these findings cannot yet be applied to humans. Further research in human subjects would be needed to determine whether hydrogen gas inhalation could be a useful treatment for TBI in people.

Abstract

Objective: To investigate the effect of hydrogen gas on NOD-like receptor protein 3 (NLRP3) inflammasomes in the cerebral cortex of rats with traumatic brain injury (TBI). Methods: 120 adult male Sprague-Dawley (SD) rates were randomly divided into 5 groups (n = 24): sham operation group (S group), TBI model group (T group), TBI+NLRP3 inhibitor MCC950 group (T+M group), TBI+hydrogen gas group (T+H group), TBI+hydrogen gas+MCC950 group (T+H+M group). TBI model was established by controlled cortical impact. NLRP3 inhibitor MCC950 (10 mg/kg) was intraperitoneally injected for 14 consecutive days before TBI operation in T+M and T+H+M groups. 2% hydrogen inhalation was given for 1 hour at 1 hour and 3 hours after TBI operation in T+H and T+H+M groups. At 6 hours after TBI operation, the pericontusional cortex tissues were obtained, the content of Evans blue (EB) was detected to evaluate the permeability of the blood-brain barrier. Water content in brain tissue was detected. The cell apoptosis was detected by TdT-mediated dUTP nick end labeling (TUNEL) and the neuronal apoptosis index was calculated. The expressions of Bcl-2, Bax, NLRP3, apoptosis-associated speck-like protein containing CARD (ASC) and caspase-1 p20 were detected by Western blotting. The levels of interleukins (IL-1β, IL-18) were detected by enzyme-linked immunosorbent assay (ELISA). Results: Compared with the S group, the content of EB in cerebral cortex, water content in brain tissue, apoptosis index and the expressions of Bax, NLRP3, ASC, caspase-1 p20 in T group were significantly increased, the expression of Bcl-2 was down-regulated, the levels of IL-1β and IL-18 were increased [the content of EB (μg/g): 87.57±6.89 vs. 10.54±1.15, water content in brain tissues: (83.79±2.74)% vs. (74.50±1.19)%, apoptotic index: (62.66±5.33)% vs. (4.61±0.96)%, Bax/β-actin: 4.20±0.44 vs. 1, NLRP3/β-actin: 3.55±0.31 vs. 1, ASC/β-actin: 3.10±0.26 vs. 1, caspase-1 p20/β-actin: 3.28±0.24 vs. 1, Bcl-2/β-actin: 0.23±0.03 vs. 1, IL-1β (ng/g): 221.58±19.15 vs. 27.15±3.27, IL-18 (ng/g): 87.26±7.17 vs. 12.10±1.85, all P < 0.05]. Compared with the T group, the T+M, T+H and T+H+M groups had significant reductions in the content of EB and water content in brain tissue, apoptotic index of the cerebral cortex, the expressions of Bax, NLRP3, and caspase-1 p20 in the brain tissue and the levels of IL-1β and IL-18, significant increases in the expression of Bcl-2. However, there was no significant difference in ASC expression. Compared with the T+H group, the content of EB in the cerebral cortex, water content in brain tissue, and apoptotic index, and the expressions of Bax, NLRP3 and caspase-1 p20 were further down-regulated in T+H+M group, the expression of Bcl-2 was further up-regulated, the levels of IL-1β and IL-18 were further decreased [the content of EB (μg/g): 40.49±3.15 vs. 51.96±4.69, water content in brain tissue: (76.58±1.04)% vs. (78.76±1.16)%, apoptotic index: (32.22±3.44)% vs. (38.54±3.89)%, Bax/β-actin: 1.92±0.16 vs. 2.56±0.21, NLRP3/β-actin: 1.94±0.14 vs. 2.37±0.24, caspase-1 p20/β-actin: 1.97±0.17 vs. 2.31±0.19, Bcl-2/β-actin: 0.82±0.07 vs. 0.52±0.04, IL-1β (ng/g): 86.23±7.09 vs. 110.44±10.48, IL-18 (ng/g): 40.18±3.22 vs. 46.23±4.02, all P < 0.05], but there were no statistical significance in all the indicators between T+M group and T+H group. Conclusions: The mechanism by which hydrogen gas alleviates TBI may be related to inhibiting NLRP3 inflammasomes in the cerebral cortex of rats.