Sulfiredoxin-1 protects spinal cord neurons against oxidative stress in the oxygen-glucose deprivation/reoxygenation model through the bax/cytochrome c/caspase 3 apoptosis pathway

BACKGROUND

Spinal cord ischemia/reperfusion injury is a common clinical, pathophysiological phenomenon with complex molecular mechanisms. Currently, there are no therapeutics available to alleviate the same. This study investigates the protective effects of sulfiredoxin-1 (Srxn 1) on spinal cord neurons following exposure to oxygen-glucose deprivation/reoxygenation (OGD/R) treatment.

MATERIALS AND METHODS

Primary spinal cord neurons were cultured, detected by anti-tubulin βⅢ, and transfected with adeno-associated virus (AAV)-Srxn 1 to overexpress Srxn 1. They were identified by their morphology and CCK-8 assay. The superoxide dismutase level was measured by superoxide dismutase assay. Malondialdehyde level was measured by malondialdehyde assay. The apoptosis ratio was calculated by Hoechst 33342 and Annexin V-PE/7-AAD staining. Mitochondrial transmembrane potential (Δψm) was detected by tetramethylrhodamine-methyl ester-perchlorate (TMRM) staining. The mRNA expression levels of Srxn 1 and caspase 3 were detected by quantitative reverse transcription-polymerase chain reaction, and the protein expression levels of Srxn 1, bax, bcl-2, cytosolic cytochrome c, and caspase 3 were detected by western blotting.

RESULTS

AAV-Srxn 1 up-regulated mRNA and protein levels of Srxn 1 in spinal cord neurons. Following exposure to OGD/R, overexpression of Srxn 1 improved the neuronal viability, alleviated the neuron apoptosis, enhanced the mitochondrial transmembrane potential, increased the SOD level, decreased the MDA level, inhibited the expression of cytosolic cytochrome c, bax, and caspase 3, and promoted the expression of bcl-2.

CONCLUSION

Srxn 1 plays a significant role in anti-apoptosis of spinal cord neurons, and Srxn 1 may be a potential therapeutic target for spinal cord I/R injury.

Wnt-3a improves functional recovery through autophagy activation via inhibiting the mTOR signaling pathway after spinal cord injury

Little is known about the effect of wnt-3a on motor nerve function and its specific molecular mechanisms after spinal cord injury (SCI). This study demonstrates that the downregulated expression levels of caspases-3, caspases-9 and chondroitin sulfate proteoglycan (CSPG) proteins and number of proportion of transferase UTP nick end labeling (TUNEL)-positive neurons by wnt-3a treatment. Then, Nissl and hematoxylin-eosin (HE) staining showed that wnt-3a significantly reduced the loss of spinal anterior horn motor neurons and promoted repair of injured spinal cord tissues after SCI. The above factors constructed a favorable microenvironment for the recovery of motor nerve function after SCI. To elucidate the molecular mechanism of neuroprotection of wnt-3a on SCI, the study showed that the expression levels of Beclin-1 and light chain (LC)3-II/I in spinal cord neurons were significantly improved by wnt-3a after SCI in vitro and vivo experiments, while the effect of wnt-3a was inhibited after mechanistic target of rapamycin (mTOR) signaling pathway being activated by MHY-1485. Besides, the level of p70S6K phosphorylation was inhibited by wnt-3a treatment, on the contrary, the level of p70S6K protein was elevated by wnt-3a, indicating that wnt-3a significantly activated neuronal autophagy by inhibiting mTOR signaling pathway after SCI. To further verify the correlation between neuroprotection of wnt-3a and autophagy, we found that after the rats and spinal cord neurons were combined treatment with wnt-3a and MHY-1485, the neuroprotection of wnt-3a on SCI was significantly inhibited. This study is the first to report that wnt-3a improves functional recovery through autophagy activation via inhibiting the mTOR signaling pathway after SCI.

Effects of propofol on glycinergic neurotransmission in a single spinal nerve synapse preparation

The effects of the intravenous anesthetic, propofol, on glycinergic transmission and on glycine receptor-mediated whole-cell currents (IGly) were examined in the substantia gelatinosa (SG) neuronal cell body, mechanically dissociated from the rat spinal cord. This "synaptic bouton" preparation, which retains functional native nerve endings, allowed us to evaluate glycinergic inhibitory postsynaptic currents (IPSCs) and whole-cell currents in a preparation in which experimental solution could rapidly access synaptic terminals. Synaptic IPSCs were measured as spontaneous (s) and evoked (e) IPSCs. The eIPSCs were elicited by applying paired-pulse focal electrical stimulation, while IGly was evoked by a bath application of glycine. A concentration-dependent enhancement of IGly was observed for ≥10µM propofol. Propofol (≥3µM) significantly increased the frequency of sIPSCs and prolonged the decay time without altering the current amplitude. However, propofol (≥3µM) also significantly increased the mean amplitude of eIPSCs and decreased the failure rate (Rf). A decrease in the paired-pulse ratio (PPR) was noted at higher concentrations (≥10µM). The decay time of eIPSCs was prolonged only at the maximum concentration tested (30µM). Propofol thus acts at both presynaptic glycine release machinery and postsynaptic glycine receptors. At clinically relevant concentrations (<1μM) there was no effect on IGly, sIPSCs or eIPSCs suggesting that at anesthetic doses propofol does not affect inhibitory glycinergic synapses in the spinal cord.

Structure-function analysis of SAP97, a modular scaffolding protein that drives dendrite growth

Activation of AMPA receptors assembled with the GluA1 subunit can promote dendrite growth in a manner that depends on its direct binding partner, SAP97. SAP97 is a modular scaffolding protein that has at least seven recognizable protein-protein interaction domains. Several complementary approaches were employed to show that the dendrite branching promoting action of full length SAP97 depends on ligand(s) that bind to the PDZ3 domain. Ligand(s) to PDZ1, PDZ2 and I3 domains also contribute to dendrite growth. The ability of PDZ3 ligand(s) to promote dendrite growth depends on localization at the plasma membrane along with GluA1 and SAP97. These results suggest that the assembly of a multi-protein complex at or near synapses is vital for the translation of AMPA-R activity into dendrite growth.