Neuroprotective mechanism of L-cysteine after subarachnoid hemorrhage

Hydrogen sulfide,which can be generated in the central nervous system from the sulfhydryl-containing amino acid,L-cysteine,by cystathionine-β-synthase,may exert protective effects in experimental subarachnoid hemorrhage;however,the mechanism underlying this effect is unknown.This study explored the mechanism using a subarachnoid hemorrhage rat model induced by an endovascular perforation technique.Rats were treated with an intraperitoneal injection of 100 mM L-cysteine(30μL)30 minutes after subarachnoid hemorrhage.At 48 hours after subarachnoid hemorrhage,hematoxylin-eosin staining was used to detect changes in prefrontal cortex cells.L-cysteine significantly reduced cell edema.Neurological function was assessed using a modified Garcia score.Brain water content was measured by the wet-dry method.L-cysteine significantly reduced neurological deficits and cerebral edema after subarachnoid hemorrhage.Immunofluorescence was used to detect the number of activated microglia.Reverse transcription-polymerase chain reaction(RT-PCR)was used to detect the levels of interleukin 1β and CD86 mRNA in the prefrontal cortex.L-cysteine inhibited microglial activation in the prefrontal cortex and reduced the mRNA levels of interleukin 1βand CD86.RT-PCR and western blot analysis of the complement system showed that L-cysteine reduced expression of the complement factors,C1q,C3αand its receptor C3aR1,and the deposition of C1q in the prefrontal cortex.Dihydroethidium staining was applied to detect changes in reactive oxygen species,and immunohistochemistry was used to detect the number of NRF2-and HO-1-positive cells.L-cysteine reduced the level of reactive oxygen species in the prefrontal cortex and the number of NRF2-and HO-1-positive cells.Western blot assays and immunohistochemistry were used to detect the protein levels of CHOP and GRP78 in the prefrontal cortex and the number of CHOP-and GRP78-positive cells.L-cysteine reduced CHOP and GRP78 levels and the number of CHOP-and GRP78-positive cells.The cystathionine-β-synthase inhibitor,aminooxyacetic acid,significantly reversed the above neuroprotective effects of L-cysteine.Taken together,L-cysteine can play a neuroprotective role by regulating neuroinflammation,complement deposition,oxidative stress and endoplasmic reticulum stress.The study was approved by the Animals Ethics Committee of Shandong University,China on February 22,2016(approval No.LL-201602022).

Localization of the hydrogen sulfide and oxytocin systems at the depth of the sulci in a porcine model of acute subdural hematoma

In the porcine model discussed in this review,the acute subdural hematoma was induced by subdural injection of autologous blood over the left parietal cortex,which led to a transient elevation of the intracerebral pressure,measured by bilateral neuromonitoring.The hematoma-induced brain injury was associated with albumin extravasation,oxidative stress,reactive astrogliosis and microglial activation in the ipsilateral hemisphere.Further proteins and injury markers were validated to be used for immunohistochemistry of porcine brain tissue.The cerebral expression patterns of oxytocin,oxytocin receptor,cystathionine-γ-lyase and cystathionine-β-synthase were particularly interesting:these four proteins all co-localized at the base of the sulci,where pressure-induced brain injury elicits maximum stress.In this context,the pig is a very relevant translational model in contrast to the rodent brain.The structure of the porcine brain is very similar to the human:the presence of gyri and sulci(gyrencephalic brain),white matter to grey matter proportion and tentorium cerebelli.Thus,pressure-induced injury in the porcine brain,unlike in the rodent brain,is reflective of the human pathophysiology.