Role of Cranial Temperature in Neuroprotection by Sodium Hydrogen Sulfide After Cardiac Arrest in Mice

FGF2 Functions in H2S's Attenuating Effect on Brain Injury Induced by Deep Hypothermic Circulatory Arrest in Rats

Deep hypothermic circulatory arrest (DHCA) can protect the brain during cardiac and aortic surgery by cooling the body, but meanwhile, temporary or permanent brain injury may arise. H2S protects neurons and the central nervous system, especially from secondary neuronal injury. We aim to unveil part of the mechanism of H2S's attenuating effect on brain injury induced by DHCA by exploring crucial target genes, and further promote the clinical application of H2S in DHCA. Nine SD rats were utilized to provide histological and microarray samples, and further the differential expression analysis. Then we conducted GO and KEGG pathway enrichment analyses on candidate genes. The protein-protein interaction (PPI) networks were performed by STRING and GeneMANIA. Crucial target genes' expression was validated by qRT-PCR and western blot. Histological study proved DHCA's damaging effect and H2S's repairing effect on brain. Next, we got 477 candidate genes by analyzing differentially expressed genes. The candidate genes were enriched in 303 GO terms and 28 KEGG pathways. Then nine genes were selected as crucial target genes. The function prediction by GeneMANIA suggested their close relation to immunity. FGF2 was identified as the crucial gene. FGF2 plays a vital role in the pathway when H2S attenuates brain injury after DHCA. Our research provides more information for understanding the mechanism of H2S attenuating brain injury after DHCA. We infer the process might probably be closely associated with immunity.

Therapeutic Hypothermia Combined with Hydrogen Sulfide Treatment Attenuated Early Blood-Brain Barrier Disruption and Brain Edema Induced by Cardiac Arrest and Resuscitation in Rat Model

Brain injury remains a major problem in patients suffering cardiac arrest (CA). Disruption of the blood-brain barrier (BBB) is an important factor leading to brain injury. Therapeutic hypothermia is widely accepted to limit neurological impairment. However, the efficacy is incomplete. Hydrogen sulfide (H2S), a signaling gas molecule, has protective effects after cerebral ischemia reperfusion injury. This study showed that combination of hypothermia and H2S after resuscitation was more beneficial for attenuated BBB disruption and brain edema than that of hypothermia or H2S treatment alone. CA was induced by ventricular fibrillation for 4 min. Hypothermia was performed by applying alcohol and ice bags to the body surface under anesthesia. We used sodium hydrosulphide (NaHS) as the H2S donor. We found that global brain ischemia induced by CA and cardiopulmonary resuscitation (CPR) resulted in brain edema and BBB disruption; Hypothermia or H2S treatment diminished brain edema, decreased the permeability and preserved the structure of BBB during the early period of CA and resuscitation, and more importantly, improved the neurologic function, increased the 7-day survival rate after resuscitation; the combination of hypothermia and H2S treatment was more beneficial than that of hypothermia or H2S treatment alone. The beneficial effects were associated with the inhibition of matrix metalloproteinase-9 expression, attenuated the degradation of the tight junction protein occludin, and subsequently protected the structure of BBB. These findings suggest that combined use of therapeutic hypothermia and hydrogen sulfide treatment during resuscitation of CA patients could be a potential strategy to improve clinical outcomes and survival rate.

Chipmunk Brain Is Resistant to Injury from Deep Hypothermic Circulatory Arrest During Cardiopulmonary Bypass

Chipmunk as a food-storing hibernator naturally undergoes hibernation that is linked to great changes in systemic physiology and could protect the central nervous system during drastically reduced cerebral blood flow and low temperature in hibernation. Deep hypothermic circulatory arrest (DHCA) is associated with neurological dysfunction. We aim to test whether the euthermic chipmunk is resistant to injury from DHCA. Sprague-Dawley (SD) rats were used in a positive control. Ten euthermic chipmunks and 10 rats were subjected to 60-minute DHCA. Sham rats and chipmunks received cannulations. The blood samples after surgery were extracted to measure the tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) level. The levels of opioid receptor delta 1 (OPRD1), mature brain-derived neurotrophic factor (m-BDNF), precursor of BDNF (pro-BDNF), TrkB, GRB2, Erk, p-Erk, P38, Bcl-2, P75NTR, TRAF6, JNK, P53, Bax, and Caspase3 of the hippocampus were analyzed at 24 hours after surgery. The brain of chipmunks and rats were fixed for histopathological assessment. In the DHCA rat group, the levels of TNF-α and IL-6 were greater (p < 0.05) compared with DHCA chipmunks. In the DHCA chipmunk group, the levels of OPRD1, mature BDNF/pro-BDNF, TrkB-FL/TrkB-T1, Bcl-2, and p-Erk/Erk of hippocampus were higher than DHCA rats. The levels of GRB2, P75NTR, TRAF6, P53, Bax, and Caspase3 in DHCA chipmunks were lower than DHCA rats. The histopathological assessment showed that the injury in DHCA rat group was more severe than the DHCA chipmunk group. Euthermic chipmunks were greatly tolerant to global cerebral injury during DHCA. Different isoforms of BDNF might be involved in the resistant strategy.