Cytokines, synaptic plasticity and network dynamics: a matter of balance

Resting-state brain network remodeling after different nerve reconstruction surgeries: a functional magnetic resonance imaging study in brachial plexus injury rats

JOURNAL/nrgr/04.03/01300535-202505000-00031/figure1/v/2024-07-28T173839Z/r/image-tiff Distinct brain remodeling has been found after different nerve reconstruction strategies, including motor representation of the affected limb. However, differences among reconstruction strategies at the brain network level have not been elucidated. This study aimed to explore intra-network changes related to altered peripheral neural pathways after different nerve reconstruction surgeries, including nerve repair, end-to-end nerve transfer, and end-to-side nerve transfer. Sprague-Dawley rats underwent complete left brachial plexus transection and were divided into four equal groups of eight: no nerve repair, grafted nerve repair, phrenic nerve end-to-end transfer, and end-to-side transfer with a graft sutured to the anterior upper trunk. Resting-state brain functional magnetic resonance imaging was obtained 7 months after surgery. The independent component analysis algorithm was utilized to identify group-level network components of interest and extract resting-state functional connectivity values of each voxel within the component. Alterations in intra-network resting-state functional connectivity were compared among the groups. Target muscle reinnervation was assessed by behavioral observation (elbow flexion) and electromyography. The results showed that alterations in the sensorimotor and interoception networks were mostly related to changes in the peripheral neural pathway. Nerve repair was related to enhanced connectivity within the sensorimotor network, while end-to-side nerve transfer might be more beneficial for restoring control over the affected limb by the original motor representation. The thalamic-cortical pathway was enhanced within the interoception network after nerve repair and end-to-end nerve transfer. Brain areas related to cognition and emotion were enhanced after end-to-side nerve transfer. Our study revealed important brain networks related to different nerve reconstructions. These networks may be potential targets for enhancing motor recovery.

Longitudinal investigation of neuroimaging changes related to memory decline in multiple sclerosis: Testing a mechanistic model

BACKGROUND

Memory decline is common in multiple sclerosis (MS), although pathophysiological mechanisms are not fully understood.

OBJECTIVE

The objective was to investigate the relationship of changes in structural and functional neuroimaging markers to memory decline over 3-year follow-up.

METHODS

Participants with MS underwent cognitive evaluation and structural, diffusion, and functional 3T magnetic resonance imaging (MRI) scans at baseline and 3-year follow-up. Changes in neuroimaging metrics from baseline to follow-up were compared between memory stable and memory decline groups. Our hypothesis that structural and functional connectivity changes mediate the association of atrophy to memory decline was tested.

RESULTS

A total of 249 MS patients completed baseline visit; 169 (67.8%) returned at 3-year follow-up. Based on ⩾10% decline, memory decline was observed in 44.4% (n = 75). Those with memory decline showed marginally greater whole-brain volume loss over time compared with those with stable memory performance (p = 0.08). In those with memory decline, changes in white matter tract integrity were related to regional cortical thinning (p < 0.01). Exploratory mediation analysis revealed structural and functional connectivity to mediate the relationship of atrophy to verbal and visual memory decline.

CONCLUSION

Further work is needed to characterize complex interrelationships of atrophy and structural/functional connectivity changes to memory decline in MS.

Mechanisms of time-restricted feeding-induced neuroprotection and neuronal plasticity in ischemic stroke as a function of circadian rhythm

Time-restricted feeding (TRF) is known to promote longevity and brain function, and potentially prevent neurological diseases. Animal studies show that TRF enhances brain-derived neurotrophic factor (BDNF) signaling and regulates autophagy and neuroinflammation, supporting synaptic plasticity, neurogenesis and neuroprotection. Feeding/fasting paradigms influence the circadian cycle, with TRF aligning circadian cycle-related gene expression, and thus altering physiological processes. Emerging evidence highlights the role of gut microbiota in neuronal plasticity, based on the observation that TRF significantly alters gut microbiota composition. Hence, the gut-brain axis may be crucial for maintaining cognitive functions and presents a potential therapeutic target for TRF-mediated neuroprotection. In the context of ischemic stroke where neuronal damage is extensive, TRF can be a preconditioning strategy to enhance synaptic plasticity and neuronal resilience, thus improving outcomes after stroke. This review discussed the link between TRF and circadian regulation in neuronal plasticity and its implications for recovery after stroke.

Mitochondria at the crossroad of dysregulated inflammatory and metabolic processes in bipolar disorders

In last few decades, considerable evidence has emphasized the significant involvement of mitochondria, often referred to as the "powerhouse of the cell," in the pathophysiology of bipolar disorder (BD). Given crucial mitochondrial functions in cellular metabolism and inflammation, both of which are compromised in BD, this perspective review examines the central role of mitochondria in inflammation and metabolism within the context of this disorder. We first describe the significance of mitochondria in metabolism before presenting the dysregulated inflammatory and metabolic processes. Then, we present a synthetic and hypothetical model of the importance of mitochondria in those dysfunctional pathways. The article also reviews different techniques for assessing mitochondrial function and discuss diagnostic and therapeutic implications. This review aims to improve the understanding of the inflammatory and metabolic comorbidities associated with bipolar disorders along with mitochondrial alterations within this context.

Immune system activation and cognitive impairment in arterial hypertension

Chronic arterial hypertension disrupts the integrity of the cerebral microvasculature, doubling the risk of age-related dementia. Despite sufficient antihypertensive therapy in still a significant proportion of individuals blood pressure lowering alone does not preserve cognitive health. Accumulating evidence highlights the role of inflammatory mechanisms in the pathogenesis of hypertension. In this review, we introduce a temporal framework to explore how early immune system activation and interactions at neurovascular-immune interfaces pave the way to cognitive impairment. The overall paradigm suggests that prohypertensive stimuli induce mechanical stress and systemic inflammatory responses that shift peripheral and meningeal immune effector mechanisms toward a proinflammatory state. Neurovascular-immune interfaces in the brain include a dysfunctional blood-brain barrier, crossed by peripheral immune cells; the perivascular space, in which macrophages respond to cerebrospinal fluid- and blood-derived immune regulators; and the meningeal immune reservoir, particularly T cells. Immune responses at these interfaces bridge peripheral and neurovascular unit inflammation, directly contributing to impaired brain perfusion, clearance of toxic metabolites, and synaptic function. We propose that deep immunophenotyping in biofluids together with advanced neuroimaging could aid in the translational determination of sequential immune and brain endotypes specific to arterial hypertension. This could close knowledge gaps on how and when immune system activation transits into neurovascular dysfunction and cognitive impairment. In the future, targeting specific immune mechanisms could prevent and halt hypertension disease progression before clinical symptoms arise, addressing the need for new interventions against one of the leading threats to cognitive health.

The Sexual Dimorphism of the Neuroimmune Response in the Brains of Taenia crassiceps-Infected Mice

BACKGROUND

Helminth infections are associated with cognitive deficits, especially in school-age children. Deworming treatment in heavily infected children improves their short- and long-term memory recall. In mice, intraperitoneal helminth infection with Taenia crassiceps (T. crassiceps) shows sexual dimorphism in terms of the parasite load, immune response, hormone levels, and behavioral changes. We have previously shown poorer short-term memory performance and changes in the concentrations of cytokines and neurotransmitters in the hippocampus, which were replicated in this study. The molecular changes in other brain structures, such as those related to reproduction, are unknown.

METHODS

Male and female Balb/cAnN mice were chronically infected with T. crassiceps larvae. We determined the peritoneal parasite load and established the presence of cytokines and neurotransmitters in the hippocampus, olfactory bulb, and hypothalamus.

RESULTS

The parasite load was higher in female than male infected mice, as expected. In the hippocampus, the neurotransmitters norepinephrine and serotonin increased in males but decreased in females. In contrast, in the olfactory bulb and hypothalamus, the neurotransmitters assessed showed no statistical differences. The cytokine profiles were different in each brain structure. The TNF-α levels in the olfactory bulb and the IL-4 levels in the hippocampus of infected mice were dimorphic; IFN-γ was augmented in both male and female infected animals, although the increase was higher in infected males.

CONCLUSIONS

The brain responds to peripheral infection with cytokine levels that vary from structure to structure. This could be a partial explanation for the dimorphic behavioral alterations associated with infection, it also demonstrates the synergic interaction between the immune, the endocrine, and the nervous systems.

Nrf2 functions as a pyroptosis-related mediator in traumatic brain injury and is correlated with cytokines and disease severity: a bioinformatics analysis and retrospective clinical study

Background

Traumatic brain injury (TBI) is a serious hazard to human health. Evidence has accumulated that pyroptosis plays an important role in brain trauma. The aim of this study is to screen potential key molecules between TBI and pyroptosis, and further explore their relationships with disease severity and cytokines.

Methods

To acquire differentially expressed genes (DEGs) before and after brain injury, the GSE89866 dataset was downloaded from the Gene Expression Omnibus (GEO) database. Meanwhile, pyroptosis-related genes were obtained from the GeneCards database, and the intersected genes were identified as differentially expressed pyroptosis-related genes (DEPGs). Moreover, the hub genes were screened via four algorithms (namely Maximum Clique Centrality, Edge Percolated Component, BottleNeck and EcCentricity) in Cytoscape software. Blood levels of Nrf2 were measured by ELISA using a commercially available kit. Finally, we further investigated the correlation between Nrf2 levels and medical indicators in TBI such as clinical characteristics, inflammatory cytokines, and severity.

Results

Altogether, we found 1,795 DEGs in GSE89866 and 98 pyroptosis-related genes in the GeneCards database. Subsequently, four hub genes were obtained, and NFE2L2 was adopted for further clinical study. By using Kruskal-Wallis test and Spearman correlation test, we found that the serum Nrf2 levels in severe TBI patients were negatively correlated with GCS scores. On the contrary, there was a positive correlation between serum Nrf2 levels and pupil parameters, Helsinki CT scores, IL-1 β and IL-18.

Conclusions

In summary, bioinformatic analyses showed NFE2L2 plays a significant role in the pathology of TBI. The clinical research indicated the increase in serum Nrf2 levels was closely related to the severity of trauma and cytokines. We speculate that serum Nrf2 may serve as a promising biochemical marker for the assessment of TBI in clinical practice.