Metformin, Rapamycin, or Nicotinamide Mononucleotide Pretreatment Attenuate Cognitive Impairment After Cerebral Hypoperfusion by Inhibiting Microglial Phagocytosis

Impaired Meningeal Lymphatics and Glymphatic Pathway in Patients with White Matter Hyperintensity

White matter hyperintensity (WMH) represents a critical global medical concern linked to cognitive decline and dementia, yet its underlying mechanisms remain poorly understood. Here, humans are directly demonstrated that high WMH burden correlates with delayed drainage of meningeal lymphatic vessels (mLVs) and glymphatic pathway. Additionally, a longitudinal cohort study reveals that glymphatic dysfunction predicts WMH progression. Next, in a rat model of WMH, the presence of impaired lymphangiogenesis and glymphatic drainage is confirmed, followed by elevated microglial activation and white matter demyelination. Notably, enhancing meningeal lymphangiogenesis through adeno-associated virus delivery of vascular endothelial growth factor-C (VEGF-C) mitigates microglial gliosis and white matter demyelination. Conversely, blocking the growth of mLVs with a VEGF-C trap strategy exacerbates these changes. The findings highlight the role of mLVs and glymphatic pathway dysfunction in aggravating brain white matter injury, providing a potential novel strategy for WMH prevention and treatment.

Unraveling the complex pathophysiology of white matter hemorrhage in intracerebral stroke: A single-cell RNA sequencing approach

AIM

This study aims to elucidate the cellular dynamics and pathophysiology of white matter hemorrhage (WMH) in intracerebral hemorrhage (ICH).

METHODS

Using varying doses of collagenase IV, a consistent rat ICH model characterized by pronounced WMH was established. Verification was achieved through behavioral assays, hematoma volume, and histological evaluations. Single-cell suspensions from the hemorrhaged region of the ipsilateral striatum on day three post-ICH were profiled using single-cell RNA sequencing (scRNA-seq). Gene Ontology (GO) and gene set variation analysis (GSVA) further interpreted the differentially expressed genes (DEGs).

RESULTS

Following WMH induction, there was a notable increase in the percentage of myeloid cells and oligodendrocyte precursor cells (OPCs), alongside a reduction in the percentage of neurons, microglia, and oligodendrocytes (OLGs). Post-ICH WMH showed homeostatic microglia transitioning into pro-, anti-inflammatory, and proliferative states, influencing lipid metabolic pathways. Myeloid cells amplified chemokine expression, linked with ferroptosis pathways. Macrophages exhibited M1 and M2 phenotypes, and post-WMH, macrophages displayed a predominance of M2 phenotypes, characterized by their anti-inflammatory properties. A surge in OPC proliferation aligned with enhanced ribosomal signaling, suggesting potential reparative responses post-WMH.

CONCLUSION

The study offers valuable insights into WMH's complex pathophysiology following ICH, highlighting the significance and utility of scRNA-seq in understanding the cellular dynamics and contributing to future cerebrovascular research.

Neuroprotective effects of oral metformin before stroke on cerebral small-vessel disease

BACKGROUND

Metformin (MET) treatment prior to stroke might have neuroprotective effects other than hypoglycemic effects. This study evaluated whether MET treatment prior to stroke is associated with neurological severity and functional outcome in patients with stroke who were not indicated for endovascular treatment and whether the effects of MET differ for each ischemic stroke subtype.

METHODS

We investigated 160 type 2 diabetes mellitus patients with ischemic stroke without endovascular treatment who were taking some oral antidiabetic agents prior to stroke in two tertiary hospitals. Lower neurological severity was defined as a National Institutes of Health Stroke Scale score of 3 or lower on admission, and favorable functional outcome was defined as a modified Rankin Scale score = 0-2 at discharge. We analyzed the effects of MET on the neurological severity and functional outcome in each ischemic stroke subtype on logistic regression analysis with adjustments for multiple confounding factors.

RESULTS

MET treatment prior to stroke was associated with lower stroke severity and favorable functional outcome. In the stroke subtypes, MET use affected both neurological severity (P = 0.037) and functional outcome (P = 0.041) in only patients with small-vessel disease (SVD).

CONCLUSIONS

MET may be useful to improve the outcome of patients with SVD.

The identification of new roles for nicotinamide mononucleotide after spinal cord injury in mice: an RNA-seq and global gene expression study

Background

Nicotinamide mononucleotide (NMN), an important transforming precursor of nicotinamide adenine dinucleotide (NAD+). Numerous studies have confirmed the neuroprotective effects of NMN in nervous system diseases. However, its role in spinal cord injury (SCI) and the molecular mechanisms involved have yet to be fully elucidated.

Methods

We established a moderate-to-severe model of SCI by contusion (70 kdyn) using a spinal cord impactor. The drug was administered immediately after surgery, and mice were intraperitoneally injected with either NMN (500 mg NMN/kg body weight per day) or an equivalent volume of saline for seven days. The central area of the spinal cord was harvested seven days after injury for the systematic analysis of global gene expression by RNA Sequencing (RNA-seq) and finally validated using qRT-PCR.

Results

NMN supplementation restored NAD+ levels after SCI, promoted motor function recovery, and alleviated pain. This could potentially be associated with alterations in NAD+ dependent enzyme levels. RNA sequencing (RNA-seq) revealed that NMN can inhibit inflammation and potentially regulate signaling pathways, including interleukin-17 (IL-17), tumor necrosis factor (TNF), toll-like receptor, nod-like receptor, and chemokine signaling pathways. In addition, the construction of a protein-protein interaction (PPI) network and the screening of core genes showed that interleukin 1β (IL-1β), interferon regulatory factor 7 (IRF 7), C-X-C motif chemokine ligand 10 (Cxcl10), and other inflammationrelated factors, changed significantly after NMN treatment. qRT-PCR confirmed the inhibitory effect of NMN on inflammatory factors (IL-1β, TNF-α, IL-17A, IRF7) and chemokines (chemokine ligand 3, Cxcl10) in mice following SCI.

Conclusion

The reduction of NAD+ levels after SCI can be compensated by NMN supplementation, which can significantly restore motor function and relieve pain in a mouse model. RNA-seq and qRT-PCR systematically revealed that NMN affected inflammation-related signaling pathways, including the IL-17, TNF, Toll-like receptor, NOD-like receptor and chemokine signaling pathways, by down-regulating the expression of inflammatory factors and chemokines.

The Combination of Citicoline and Nicotinamide Mononucleotide Induces Neurite Outgrowth and Mitigates Vascular Cognitive Impairment via SIRT1/CREB Pathway

Vascular dementia (VD) is characterized with vascular cognitive impairment (VCI), which currently has few effective therapies in clinic. Neuronal damage and white matter injury are involved in the pathogenesis of VCI. Citicoline has been demonstrated to exhibit neuroprotection and neurorepair to improve cognition in cerebrovascular diseases. Nicotinamide adenine dinucleotide (NAD+)-dependent sirtuin (SIRT) signaling pathway constitutes a strong intrinsic defense system against various stresses including neuroinflammation in VCI. Our hypothesis is that the combined use of citicoline and the precursor of NAD+, nicotinamide mononucleotide (NMN), could enhance action on cognitive function in VCI. We investigated the synergistic effect of these two drugs in the rat model of VCI by bilateral common carotid artery occlusion (BCCAO). Citicoline significantly enhanced neurite outgrowth in Neuro-2a cells, and the combination of citicoline and NMN remarkably induced neurite outgrowth in Neuro-2a cells and primary cortical neuronal cells with an optimal proportion of 4:1. In the rat model of BCCAO, when two drugs in combination of 160 mg/kg citicoline and 40 mg/kg NMN, this combination administrated at 7 days post-BCCAO significantly improved the cognitive impairment in BCCAO rats compared with vehicle group by the analysis of the Morris water maze and the novel object recognition test. This combination also decreased microglial activation and neuroinflammation, and protected white matter integrity indicated by the increased myelin basic protein (MBP) expression through activation of SIRT1/TORC1/CREB signaling pathway. Our results suggest that the combination of citicoline and NMN has a synergistic effect for the treatment of VD associated with VCI.