Pathological alterations and stress responses near DBS electrodes after MRI scans at 7.0T, 3.0T and 1.5T: an in vivo comparative study

VEGF-A ameliorates ischemia hippocampal neural injury via regulating autophagy and Akt/CREB signaling in a rat model of chronic cerebral hypoperfusion

OBJECTIVE

Chronic cerebral hypoperfusion (CCH) can cause a series of pathophysiological processes, including neuronal autophagy and apoptosis. VEGF-A has been reported to affect angiogenesis and neurogenesis in many CNS diseases. However, its effects on neuronal autophagy and apoptosis, as well as the underlying mechanisms in CCH remain unclear.

METHODS

To address these issues, the CCH model was established by permanent bilateral common carotid artery occlusion (2VO). Rats were sacrificed at different stages of CCH. Hippocampal morphological and ultrastructural changes were detected using HE staining and electron microscopy. The immunoreactivities of microtubule-associated protein 1 light chain 3 (LC3) and phospho-cAMP response element binding protein (p-CREB) were examined by immunofluorescence staining. The neuronal apoptosis was detected via TUNEL staining. The levels of LC3-II, Beclin-1, Akt, p-Akt, CREB, p-CREB, Caspase-3, and Bad were accessed by Western blotting. Furthermore, mouse hippocampal HT22 neurons received the oxygen and glucose deprivation (OGD) treatment, VEGF-A treatment, and GSK690693 (an Akt inhibitor) treatment, respectively.

RESULTS

LC3-II protein started to increase at 3 days of CCH, peaked at 4 weeks of CCH, then decreased. CCH increased the levels of LC3-II, Caspase-3, and Bad, and decreased the levels of p-Akt, CREB, and p-CREB, which were reversed by VEGF-A treatment. VEGF-A also improved CCH-induced neuronal ultrastructural injuries and apoptosis in the hippocampus in vitro. In HT22, the anti-apoptosis and pro-phosphorylation of VEGF-A were reversed by GSK690693.

CONCLUSION

Present results provide a novel neuroprotective effect of VEGF-A in CCH that is related to the inhibition of neuronal autophagy and activation of the Akt/CREB signaling, suggesting a potential therapeutic strategy for ischemic brain damage.

Tetramethylpyrazine promotes stroke recovery by inducing the restoration of neurovascular unit and transformation of A1/A2 reactive astrocytes

2,3,5,6-Tetramethylpyrazine (TMP) as an active ingredient extracted from a traditional Chinese herbal medicine Ligusticum chuanxiong Hort. has been proved to penetrate blood-brain barrier (BBB) and show neuroprotective effects on cerebral ischemia. However, whether TMP could regulate astrocytic reactivity to facilitate neurovascular restoration in the subacute ischemic stroke needs to be urgently verified. In this research, permanent occlusion of the middle cerebral artery (MCAO) model was conducted and TMP (10, 20, 40 mg/kg) was intraperitoneally administrated to rats once daily for 2 weeks. Neurological function was evaluated by motor deficit score (MDS). Magnetic resonance imaging (MRI) was implemented to analyze tissue injury and cerebral blood flow (CBF). Magnetic resonance angiography (MRA) was applied to exhibit vascular signals. Transmission electron microscopy (TEM) was performed to detect the neurovascular unit (NVU) ultrastructure. Haematoxylin and eosin (HE) staining was utilized to evaluate cerebral histopathological lesions. The neurogenesis, angiogenesis, A1/A2 reactivity, aquaporin 4 (AQP4) and connexin 43 (Cx43) of astrocytes were observed with immunofluorescent staining. Then FGF2/PI3K/AKT signals were measured by western blot. Findings revealed TMP ameliorated neurological functional recovery, preserved NVU integrity, and enhanced endogenous neurogenesis and angiogenesis of rats with subacute ischemia. Shifting A1 to A2 reactivity, suppressing excessive AQP4 and Cx43 expression of astrocytes, and activating FGF2/PI3K/AKT pathway might be potential mechanisms of promoting neurovascular restoration with TMP after ischemic stroke.

Diffusion-weighted 7.0T Magnetic Resonance Imaging in Assessment of Intervertebral Disc Degeneration in Rats

Background:

Intervertebral disc degeneration (IDD) is a major cause of disc protrusion, likely to be associated with decrease of water content. This research aimed to evaluate IDD by diffusion-weighted imaging (DWI) with a 7.0 Tesla (T) magnetic resonance imaging (MRI) machine.

Methods:

A total of 24 healthy Sprague-Dawley rats were randomly selected and divided into four groups (A, B, C, and D), each consisting of 3 male and 3 female rats (28, 42, 56, and 70 days old, respectively). All the rats were imaged with a 7.0T MRI, producing T2WI, T1WI, and functional DWI sequences. Data were collected and apparent diffusion coefficient (ADC) charts were constructed. Nucleus pulposus and annulus fibrosus regions were identified, several regions of interest were chosen, and their ADC values were obtained. After imaging, rats were sacrificed and their intervertebral discs (L1–L6) were dissected, yielding a total of 144 discs. Protein was extracted for the purpose of Western blotting. Comparison among multiple samples used one-way analysis of variance and least significant difference methods.

Results:

7.0T MRI revealed evident decrease in signal intensity within intervertebral discs of Sprague-Dawley rats with age. Intervertebral disc ADC values significantly decreased from Group A (0.00154 ± 0.00008) to Group D (0.00107 ± 0.00007; P < 0.01); nucleus pulposus ADC values significantly decreased from Group A (0.00164 ± 0.00005) to Group D (0.00140 ± 0.00007; P < 0.01) and annulus fibrosus ADC values significantly decreased from Group A (0.00129 ± 0.00014) to Group D (0.00082 ± 0.00012; P < 0.01). Meanwhile, it also revealed evident decrease from high spinal level to low spinal level: nucleus pulposus ADC values in Group A significantly decreased from L1/L2 (0.00163 ± 0.00006) to L6/S1 (0.00139 ± 0.00004; P < 0.01). While annulus fibrosus ADC values did not differ significantly between levels in Group A (P > 0.05). Western blotting showed that aggrecan content of intervertebral discs decreased from Group A (1.88 ± 0.16) to Group D (0.17 ± 0.04) with age (P < 0.01); Type II collagen content of intervertebral discs decreased from Group A (2.22 ± 0.04) to Group D (0.20 ± 0.01) with age (P < 0.01). No significant differences in aggrecan and Type II collagen content of L1–L6 intervertebral discs in Group A were noted (P > 0.05). Mean ADC values of different intervertebral regions were positively correlated with aggrecan and Type II collagen content (aggrecan: r = 0.631, P < 0.01; Type II collagen: r = 0.680, P < 0.01).

Conclusion:

7.0T MRI-DWI could be applied to effectively diagnose and research early IDD in tiny variations.

Ultrahigh-Magnitude Brain Magnetic Resonance Imaging Scan on Rhesus Monkeys With Implanted Deep Brain Stimulation Hardware

BACKGROUND

Patients with implanted deep brain stimulation (DBS) hardware are prohibited from undergoing magnetic resonance imaging (MRI) scans at magnitudes greater than 1.5 T to avoid potential MRI-related heating injury. Whether DBS devices are compatible with higher field MRI scanning is unknown. This study aimed to investigate whether 7.0 T and 3.0 T MRI scans can be safely performed on rhesus monkeys with implanted DBS devices.

METHODS

Eight male rhesus monkeys were included in this study and stereotactically implanted with DBS devices in the left anterior thalamus. Two weeks after DBS device implantation, 7.0 T and 3.0 T MRI scans were performed. The monkeys were observed for 72 hours. After explantation of the DBS system, 7.0 T MRI was repeated to determine potential lesions. Hematoxylin and eosin staining and transmission electron microscopy were conducted to assess pathological alterations.

RESULTS

In both groups, the monkeys exhibited no behavioral changes related to neurological deficits. Post-explantation MRI showed no malacia foci surrounding the DBS tracks. Additionally, neither hematoxylin and eosin staining nor transmission electron microscopy showed clear injury near the DBS leads.

CONCLUSION

These results indicate that no obvious heating injury was induced in the tissue surrounding the DBS leads by the 7.0 T and 3.0 T MRI scans. Although the results of this study may not be generalizable, these data suggest that patients with implanted DBS devices can undergo even 7.0 T MRI without risk of brain injury.

Inhibition of SENP3 by URB597 ameliorates neurovascular unit dysfunction in rats with chronic cerebral hypoperfusion

Disruption of the neurovascular unit (NVU), induced by chronic cerebral hypoperfusion (CCH), has been broadly found in various neurological disorders. SUMO-specific protease 3 (SENP3) is expressed in neurons, astrocytes, and microglia, and regulates a variety of cell events. However, whether SENP3 is involved in neurovascular injury under the condition of CCH is still elusive. To address this issue, we investigated the effect of the fatty acid amide hydrolase (FAAH) inhibitor URB597 on NVU and the role of SENP3 in this process, as well as the underling mechanisms. The expression of SENP3 was detected by immunochemistry. The function and structure of the NVU was assessed by Western blot analysis and transmission electron microscopy. CCH caused the upregulation of SENP3, the disruption of cell and non-cell components at the protein level within the NVU, and ultrastructural deterioration. The NVU impairment as well as overexpression of SENP3 were reversed by treatment with URB597. These results reveal a novel neuroprotective role in URB597, which implicates URB597 in the amelioration of CCH-induced NVU impairment by inhibiting SENP3.

Deep brain stimulation of the anterior nucleus of the thalamus reverses the gene expression of cytokines and their receptors as well as neuronal degeneration in epileptic rats

BACKGROUND

Deep brain stimulation of the anterior nucleus of the thalamus (ANT-DBS) is effective in seizure control. However, the mechanisms remain unclear.

METHODS

Sixty-four rats were randomly assigned to the control group, the kainic acid (KA) group, the sham-DBS group and the DBS group. Video-electroencephalogram (EEG) was used to monitor seizures. Quantitative real time PCR (qPCR) was applied for detecting interleukin-1 beta (IL-1β), IL-1 receptor (IL-1R), IL-6, IL-6 receptor (IL-6R), gp130, tumor necrosis factor-alpha (TNF-α), TNF-receptor 1 (TNF-R1) and TNF-receptor 2 (TNF-R2) expression 12h after the establishment of an epileptic model. The neuronal structural degeneration in the hippocampus was evaluated with transmission electron microscopy (TEM) at this same time point.

RESULTS

The seizure frequency was 48.6% lower in the DBS group compared with the sham-DBS group (P<0.01). The expression of IL-1β, IL-1R, IL-6, IL-6R, gp130, TNF-α and TNF-R1 was elevated in both the KA and the sham group compared with the control group (all Ps<0.01). Additionally, ANT-DBS was able to reverse this gene expression pattern in the DBS group compared with the sham-DBS group (all Ps<0.01). There was no significant difference in TNF-R2 expression among the four groups. The neuronal structural degeneration in the KA group and the sham-DBS group was more severe than that in the control group (injury scores, all Ps<0.01). ANT-DBS was also capable of relieving the degeneration compared with the sham-DBS group (injury score, P<0.01).

CONCLUSIONS

This study demonstrated that ANT-DBS can reduce seizure frequency in the early stage in epileptic rats as well as relieve the pro-inflammatory state and neuronal injury, which may be one of the most effective mechanisms of ANT-DBS against epileptogenesis.

Ceruloplasmin is an endogenous protectant against kainate neurotoxicity

To determine the role of ceruloplasmin (Cp) in epileptic seizures, we used a kainate (KA) seizure animal model and examined hippocampal samples from epileptic patients. Treatment with KA resulted in a time-dependent decrease in Cp protein expression in the hippocampus of rats. Cp-positive cells were colocalized with neurons or reactive astrocytes in KA-treated rats and epileptic patient samples. KA-induced seizures, initial oxidative stress (i.e., hydroxyl radical formation, lipid peroxidation, protein oxidation, and synaptosomal reactive oxygen species), altered iron status (increasing Fe(2+) accumulation and L-ferritin-positive reactive microglial cells and decreasing H-ferritin-positive neurons), and impaired glutathione homeostasis and neurodegeneration (i.e., Fluoro-Nissl and Fluoro-Jade B staining analyses) were more pronounced in Cp antisense oligonucleotide (ASO)- than in Cp sense oligonucleotide-treated rats. Consistently, Cp ASO facilitated KA-induced lactate dehydrogenase (LDH) release, Fe(2+) accumulation, and glutathione loss in neuron-rich and mixed cultures. However, Cp ASO did not alter KA-induced LDH release or Fe(2+) accumulation in the astroglial culture, but did facilitate impairment in glutathione homeostasis in the same culture. Importantly, treatment with human Cp protein resulted in a significant attenuation against these neurotoxicities induced by Cp ASO. Our results suggest that Cp-mediated neuroprotection occurs via the inhibition of seizure-associated oxidative damage (including impairment in glutathione homeostasis), Fe(2+) accumulation, and alterations in ferritin immunoreactivity. Moreover, interactive modulation between neurons and glia was found to be important for Cp upregulation in the attenuation of epileptic damage in both animals and humans.