Effects of transcranial direct current stimulation on brain cytokine levels in rats

Reduced plasma interleukin-6 concentration after transcranial direct current stimulation to the prefrontal cortex

OBJECTIVES

Transcranial direct stimulation (tDCS) targeted to the dorsolateral prefrontal cortex (DLPFC) reduces food intake and hunger, but its effects on circulating factors are unclear. We assessed the effect of repeated administration of tDCS to the left DLPFC (L-DLPFC) on concentrations of pro/anti-inflammatory and appetitive hormone concentrations.

MATERIALS AND METHODS

Twenty-nine healthy adults with obesity (12 M; 42±11 y; BMI=39±8 kg/m2) received 3 consecutive inpatient sessions of either anodal or sham tDCS targeted to the L-DLPFC during a period of ad libitum food intake. Fasting plasma concentrations of IL-6, orexin, cortisol, TNF-α, IL-1β, ghrelin, PYY, and GLP-1 were measured before the initial and after the final tDCS sessions.

RESULTS

IL-6 (β=-0.92 pg/ml p=0.03) decreased in the anodal group compared with sham, even after adjusting for kcal intake; there were no changes in other hormones. Mean kcal intake was associated with higher IL-1β and ghrelin concentrations after the ad libitum period (β=0.00018 pg/ml/kcal, p=0.03; β=0.00011 pg/ml/kcal, p=0.02; respectively), but not differ by intervention groups.

CONCLUSIONS

IL-6 concentrations were reduced following anodal tDCS to the L-DLPFC independent of ad libitum intake. IL-6 concentrations reflect the inflammatory state of adiposity and may affect eating behavior and weight gain. These findings provide evidence of therapeutic benefit of tDCS.

Transcranial direct current stimulation combined with swimming exercise improves the learning and memory abilities of vascular dementia rats by regulating microglia through miR-223-3p/PRMT8

BACKGROUND

Vascular dementia (VD) is the second most common type of dementia worldwide. Previous studies have proven that transcranial direct current stimulation (tDCS) has potential applications in relieving cognitive impairment in VD animal models. The purpose of this study was to probe the mechanism by which tDCS combined with swimming exercise improves the learning and memory abilities of VD model rats.

METHOD

The VD rat model was induced using the permanent bilateral common carotid artery occlusion (2-VO) method; tDCS was applied to the rats and then they took part in swimming exercises. Rat memory, platform crossing time, and platform crossing frequency were analyzed via a water maze experiment. Nerve damage in the cortex and hippocampal CA1 area of the rats was observed using Nissl staining. Western blotting, immunohistochemistry, immunofluorescence staining and reverse transcription quantitative polymerase chain reaction (RT - qPCR) were used to determine the expression of related proteins and genes. The levels of oxidative stress were detected by kits.

RESULTS

We demonstrated that VD model rats treated with tDCS combined with swimming exercise exhibited significant improvement in memory, and VD model rats exhibited significantly reduced neuronal loss in the hippocampus, and reduced microglial activation and M1 polarization. tDCS combined with swimming exercise protects VD model rats from oxidative stress through the miR-223-3p/protein arginine methyltransferase 8 (PRMT8) axis and inhibits the activation of the TLR4/NF-κB signaling pathway.

CONCLUSION

Our results suggest that tDCS combined with swimming exercise improved the learning and memory ability of VD model rats by regulating the expression of PRMT8 through miR-223-3p to affect microglial activation and M1 polarization.

Combined repetitive transcranial magnetic stimulation and gut microbiota modulation through the gut-brain axis for prevention and treatment of autism spectrum disorder

Autism spectrum disorder (ASD) encompasses a range of neurodevelopmental conditions characterized by enduring impairments in social communication and interaction together with restricted repetitive behaviors, interests, and activities. No targeted pharmacological or physical interventions are currently available for ASD. However, emerging evidence has indicated a potential association between the development of ASD and dysregulation of the gut-brain axis. Repetitive transcranial magnetic stimulation (rTMS), a noninvasive diagnostic and therapeutic approach, has demonstrated positive outcomes in diverse psychiatric disorders; however, its efficacy in treating ASD and its accompanying gastrointestinal effects, particularly the effects on the gut-brain axis, remain unclear. Hence, this review aimed to thoroughly examine the existing research on the application of rTMS in the treatment of ASD. Additionally, the review explored the interplay between rTMS and the gut microbiota in children with ASD, focusing on the gut-brain axis. Furthermore, the review delved into the integration of rTMS and gut microbiota modulation as a targeted approach for ASD treatment based on recent literature. This review emphasizes the potential synergistic effects of rTMS and gut microbiota interventions, describes the underlying mechanisms, and proposes a potential therapeutic strategy for specific subsets of individuals with ASD.

Anti-Inflammatory and Cortical Responses after Transcranial Direct Current Stimulation in Disorders of Consciousness: An Exploratory Study

Disorders of consciousness (DoC) due to severe traumatic brain injury (TBI) are associated with severe disability and an alteration of cortical activation, angiogenesis, and inflammation, which are crucial elements for behavioural recovery. This exploratory study aimed to evaluate anti-inflammatory and cortical responses after transcranial direct current stimulation (tDCS) in traumatic prolonged disorders of consciousness. Ten minimally conscious state (MCS) patients underwent ten sessions of anodal tDCS (five sessions/week, two weeks, 40 min/session) on the primary motor cortex bilaterally. Clinical evaluations were performed using the Coma Recovery Scale-Revised (CRS-R) pre- and post-treatment. In contrast, after single and multiple tDCS sessions, the haemodynamic cortical response was obtained with functional near-infrared spectroscopy (fNIRS). Moreover, angiogenesis (angiopoietin-2, BMP9, endoglin, HbEFG, HGF, IL8, Leptin, PLGF, VEGF-A, and VEGF-C) and inflammation (GM-CSF, IFNg, IP10, MCP1, and TNFα) circulating biomarkers were collected. A significant haemodynamic response was observed after a single tDCS session, with an increased activation from 4.4 (3.1-6.1) to 7.6 (2.9-15.7) a.u. (p = 0.035). After ten tDCS sessions, a significant reduction of angiopoietin-2, VEGF-C, and IP-10 was detected. Moreover, a correlation between behavioural (CRS-R), TNFα (r = 0.89; p = 0.007), and IP10 (r = 0.81; p = 0.014) variation was found. In conclusion, a single tDCS session can increase the cortical activation in MCS patients. Moreover, multiple tDCS sessions showed an anti-inflammatory effect related to behavioural improvement.

Transcranial Direct Current Stimulation Attenuates the Chronic Pain of Osteoarthritis in Rats via Reducing NMDAR2B Expressions in the Spinal Cord

OBJECTIVES

Osteoarthritis (OA) has been the common cause to lead to chronic pain. Transcranial direct current stimulation (tDCS) is effective in the treatment of chronic pain, but its analgesic mechanism is still unclear. This study observed the analgesic effects of tDCS in rats to explore the top-down analgesic modulation mechanism of tDCS.

METHODS

Monosodium iodoacetate (MIA) was used to establish OA chronic pain model. After 21 days, the rats received tDCS for 14 consecutive days (20 min/day). We assessed the pain-related behaviors of rats at different time points. Western blot and Immunohistochemistry were performed to observe the expression level of NMDAR2B in the spinal cord after tDCS treatment.

RESULTS

After MIA injection, rats developed apparent mechanical hyperalgesia and thermal hyperalgesia. However, the pain-related behaviors of rats were significantly improved after tDCS treatment. In addition, the expression of NMDAR2B and the proportion of positive stained cells of NMDAR2B were reversed by tDCS treatment.

CONCLUSIONS

The results demonstrated that tDCS can attenuate OA-induced chronic pain in rats via reducing NMDAR2B expressions in the spinal cord. We believe that this may be the result of tDCS participating in the top-down modulation of pain pathway in the endogenous analgesic system.