Ubiquitin and endogenous antioxidant enzymes participate in neuroprotection of the rabbit spinal cord after ischemia and bradykinin postconditioning

The neuroprotective effect and RNA-sequence analysis of postconditioning on the ischemic stroke with diabetes mellitus tree shrew model

INTRODUCTION

Patients with comorbidity of ischemic stroke (IS) and diabetes mellitus (DM) show poor neurological functional recovery, and ischemic postconditioning (IPOC) should be considered a powerful neuroprotective method for IS. However, whether it should be introduced for patients with IS and DM remains controversial. This study established a DM with IS (DMIS) tree shrew model, which was intervened by IPOC to assess its neuroprotective effects and also to analyze the relevant mechanism by RNA-sequence and bioinformatics analysis.

METHODS

Fifty-four tree shrews were randomly divided into a sham operation control group, a DMIS group, and an IPOC group (DMIS model), with 18 tree shrews per group. Triphenyl tetrazolium chloride (TTC), hematoxylin-eosin (HE) staining, transmission electron microscopy (TEM), and RNA-sequence analysis were performed to assess the IPOC effect.

RESULTS

IPOC reduced infarct size and reduced nerve cell injury in IS tree shrews with DM. RNA-seq analysis showed that IPOC significantly increased the expression of the homeobox protein SIX3, while downregulating the expression of HLA class II histocompatibility antigens DQ beta 1 chain, CAS1 domain-containing protein 1, and cytokine receptor-like factor 2. The most downregulated signaling pathways include the NF-κB signaling pathway, TNF signaling pathway, and Fc gamma R-mediated phagocytosis.

CONCLUSIONS

IPOCs have a neuroprotective effect in a DMIS animal model that reduces infarct size and nerve cell injury. This mechanism might be related to reducing inflammation and stress responses that decreases the activity of TNF and NF-κB signaling pathways.

Induction of ischemic tolerance by remote perconditioning or postconditioning as neuroprotective strategy for spinal cord motor neurons

AIMS

The study is focused on the investigation of the mechanisms leading to ischemic tolerance acquisition in the spinal cord neurons via application of non-invasive method of remote conditioning.

MATERIAL AND METHODS

We have verified the possibility of neuroprotection of spinal cord in rabbit by using remote perconditioning (PerC) applied during last 12 min of spinal cord ischemia (SC-ischemia) or postconditioning (PostC) applied after 1st (early) or 3rd (late) h of reperfusion. Spinal cord ischemia was induced by occlusion of the aorta below the left renal artery for 20 min. Reperfusion period was 24 or 72 h. Remote conditioning was induced by compression of left forelimb with a tourniquet in 3 cycles of 2 min of ischemia, each followed by 2 min of reperfusion. Damaged neurons were detected by Fluoro Jade B method and the modified Tarlov score was used for functional assessment.

KEY FINDINGS

The remote conditioning significantly attenuated degeneration of motor neurons in all remote conditioned groups versus both SC-ischemia groups. We detected significant changes in number of Hsp70 positive motor neurons. At 72time point, in the group with remote late PostC we observed significant increase (p < 0.001) of Hsp70 positive motor neurons versus SC- ischemia group and sham control. There was a trend towards improvement of hindlimbs movement.

SIGNIFICANCE

This study showed the effectiveness of remote conditioning as a neuroprotective strategy, evidenced by induction of ischemic tolerance leading to decrease of motor neuron degeneration.

Bradykinin Activates the Bradykinin B2 Receptor to Ameliorate Neuronal Injury in a Rat Model of Spinal Cord Ischemia-Reperfusion Injury

Bradykinin and bradykinin B2 receptors (B2R) play important roles in both the peripheral and central nervous systems. The aim of this study was to explore the changes of bradykinin and B2R in spinal cord ischemic injury (SCII) and whether bradykinin treatment would improve the neurologic function of SCII rats. The rats were divided into the sham group, the SCII group, and three doses of bradykinin (50, 100, 150 μg/kg) groups. The neurologic function was assessed by the Basso, Beattie, and Bresnahan (BBB) score at -1, 1, 3, 5, and 7 days postsurgery. Bradykinin concentration in serum and IL-6, TNF-α, and MCP-1 levels in the spinal cord were detected by ELISA. The mRNA expressions of B2R, IL-6, TNF-α, MCP-1, COX-2, and iNOS in the spinal cord were determined by RT-PCR. The protein expressions of B2R, COX-2, iNOS, p65, and p-p65 were detected by Western blot. Immunohistochemical staining was used to examine B2R expression in the L4-6 segments of the spinal cord. Bradykinin levels in serum and B2R expression in the spinal cord were downregulated in SCII rats. Bradykinin treatment significantly improved the hind limb motor function of SCII rats and increased B2R expression, inhibiting COX-2, iNOS, and p-p65 expression in the spinal cord of SCII rats together with a decrease of the inflammatory mediators of IL-6, TNF-α, and MCP-1 levels. Bradykinin administration activated B2R in the spinal cord of SCII rats, which may improve hind limb locomotor recovery by regulating the NF-κB signaling pathway to inhibit the inflammatory response. These findings may provide a theoretical basis for the clinical application of bradykinin in SCII.

Therapeutic Hypothermia Improves Hind Limb Motor Outcome and Attenuates Oxidative Stress and Neuronal Damage in the Lumbar Spinal Cord Following Cardiac Arrest

Hypothermia enhances outcomes of patients after resuscitation after cardiac arrest (CA). However, the underlying mechanism is not fully understood. In this study, we investigated effects of hypothermic therapy on neuronal damage/death, microglial activation, and changes of endogenous antioxidants in the anterior horn in the lumbar spinal cord in a rat model of asphyxial CA (ACA). A total of 77 adult male Sprague–Dawley rats were randomized into five groups: normal, sham ACA plus (+) normothermia, ACA + normothermia, sham ACA + hypothermia, and ACA + hypothermia. ACA was induced for 5 min by injecting vecuronium bromide. Therapeutic hypothermia was applied after return of spontaneous circulation (ROSC) via rapid cooling with isopropyl alcohol wipes, which was maintained at 33 ± 0.5 °C for 4 h. Normothermia groups were maintained at 37 ± 0.2 °C for 4 h. Neuronal protection, microgliosis, oxidative stress, and changes of endogenous antioxidants were evaluated at 12 h, 1 day, and 2 days after ROSC following ACA. ACA resulted in neuronal damage from 12 h after ROSC and evoked obvious degeneration/loss of spinal neurons in the ventral horn at 1 day after ACA, showing motor deficit of the hind limb. In addition, ACA resulted in a gradual increase in microgliosis with time after ACA. Therapeutic hypothermia significantly reduced neuronal loss and attenuated hind limb dysfunction, showing that hypothermia significantly attenuated microgliosis. Furthermore, hypothermia significantly suppressed ACA-induced increases of superoxide anion production and 8-hydroxyguanine expression, and significantly increased superoxide dismutase 1 (SOD1), SOD2, catalase, and glutathione peroxidase. Taken together, hypothermic therapy was found to have a substantial impact on changes in ACA-induced microglia activation, oxidative stress factors, and antioxidant enzymes in the ventral horn of the lumbar spinal cord, which closely correlate with neuronal protection and neurological performance after ACA.