Alzheimer's disease (AD) is the most common form of dementia in the elderly, causing neuronal degeneration and cognitive deficits that significantly impair independence and quality of life for those affected and their families. Though AD is a major neurodegenerative disease with vast avenues of investigation, there is no effective treatment to cure AD or slow disease progression. The present work evaluated the therapeutic effect of long-term photobiomodulation (PBM) treatment with continuous-wave low-level laser on AD and its underlying mechanism. Methods: PBM was implemented for 2 min, 3 times per week for 16 months in 2-month-old transgenic AD rats. A battery of behavioral tests was performed to measure the effect of PBM treatment on cognitive dysfunction in AD rats. The effects of PBM therapy on typical AD pathologies, including amyloid plaques, intracellular neurofibrillary tangles, neuronal loss, neuronal injury, neuronal apoptosis, and neurodegeneration, were then assessed. The underlying mechanisms were measured using immunofluorescence staining, western blotting analysis, mass spectrometry, primary cortical and hippocampal cell cultures, and related assay kits. Results: PBM treatment significantly improved the typical AD pathologies of memory loss, amyloid plaques, tau hyperphosphorylation, neuronal degeneration, spine damage, and synaptic loss. PBM treatment had several mechanistic effects which may explain these beneficial effects, including 1) regulation of glial cell polarization and inhibition of neuroinflammation, 2) preservation of mitochondrial dynamics by regulating fission and fusion proteins, and 3) suppression of oxidative damage to DNA, proteins, and lipids. Furthermore, PBM enhanced recruitment of microglia surrounding amyloid plaques by improving the expression of microglial IL-3Rα and astrocytic IL-3, which implies a potential role of PBM in improving Aβ clearance. Finally, our results implicate neuronal hemoglobin in mediating the neuroprotective effect of PBM, as Hbα knockdown abolished the neuroprotective effect of PBM treatment. Conclusion: Collectively, our data supports the potential use of PBM treatment to prevent or slow the progression of AD and provides new insights into the molecular mechanisms of PBM therapy.

Rationale: Previous work has indicated that continuous theta-burst stimulation (cTBS), a modality of transcranial magnetic stimulation (TMS), may provide neuroprotection and improve neurological function after stroke by preserving the blood-brain barrier, altering glial polarization phenotypes, and supporting peri-infarct angiogenesis. The present study was performed to examine whether cTBS, a noninvasive neurostimulation technique, promotes neurogenesis in a photothrombotic (PT) stroke rat model and contributes to functional recovery. Methods: Beginning 3 h or 1 week after the induction of PT stroke, once-daily 5-min cTBS treatments were applied to the infarcted hemisphere for 6 days. Samples were collected 6 days, 22 days, and 35 days after PT stroke. Fluorescent labeling, Western blotting, and behavioral tests were performed accordingly. Results: We found that cTBS therapy significantly expanded the pool of neural progenitor cells (NPCs) and newly generated immature neurons in the cortical peri-infarct region after PT stroke. Likewise, the amount of DCX-positive immature neurons in the peri-infarct area was markedly elevated by cTBS. Application of cTBS strikingly diminished the PT-induced loss of NPCs and newly-formed neurons. In addition, the amount of newly generated mature neurons in the peri-infarct zone was significantly promoted by cTBS. Intriguingly, cTBS reduced reactive gliogenesis significantly while promoting oligodendrogenesis and preserving myelination. Mechanistic studies uncovered that cTBS upregulated brain-derived neurotrophic factor (BDNF) and fibroblast growth factor 2 (FGF2). Finally, cTBS-treated animals displayed improved motor functions. To be noted, temozolomide (TMZ), a drug that has been previously used to suppress neurogenesis, could reverse the beneficial effects of cTBS. Conclusions: Our findings provide new insight into the mechanism by which cTBS promotes functional recovery from stroke. We demonstrated that cTBS effectively enhances and sustains neurogenesis after PT stroke. Both early and delayed cTBS treatment could improve the survival of newly generated neurons and functional recovery, and inhibition of neurogenesis could reverse these therapeutic benefits. Mechanistically, cTBS was effective in upregulating the release of neurotrophic factors, protecting NPC and immature neurons, as well as suppressing excessive gliogenesis.

Rationale: The integrity and function of the blood-brain barrier (BBB) is compromised after stroke. The current study was performed to examine potential beneficial effects and underlying mechanisms of repetitive transcranial magnetic stimulation (rTMS) on angiogenesis and vascular protection, function, and repair following stroke, which are largely unknown. Methods: Using a rat photothrombotic (PT) stroke model, continuous theta-burst rTMS was administered once daily to the infarcted hemisphere for 5 min, beginning 3 h after PT stroke. This treatment was applied for 6 days. BBB integrity, blood flow, vascular associated proteins, angiogenesis, integrity of neuronal morphology and structure, and behavioral outcome were measured and analyzed at 6 and/or 22 days after PT stroke. Results: We report that rTMS significantly mitigated BBB permeabilization and preserved important BBB components ZO-1, claudin-5, occludin, and caveolin-1 from PT-induced degradation. Damage to vascular structure, morphology, and perfusion was ameliorated by rTMS, resulting in improved local tissue oxygenation. This was accompanied with robust protection of critical vascular components and upregulation of regulatory factors. A complex cytokine response was induced by PT, particularly at the late phase. Application of rTMS modulated this response, ameliorating levels of cytokines related to peripheral immune cell infiltration. Further investigation revealed that rTMS promoted and sustained post-ischemic angiogenesis long-term and reduced apoptosis of newborn and existing vascular endothelial cells. Application of rTMS also inhibited PT-induced excessive astrocyte-vasculature interactions and stimulated an A1 to A2 shift in vessel-associated astrocytes. Mechanistic studies revealed that rTMS dramatically increased levels of PDGFRβ associated with A2 astrocytes and their adjacent vasculature. As well, A2 astrocytes displayed marked amplification of the angiogenesis-related factors VEGF and TGFβ. PT induced a rise in vessel-associated expression of HIF-1α that was starkly intensified by rTMS treatment. Finally, rTMS preserved neuronal morphology, synaptic structure integrity and behavioral outcome. Conclusions: These results indicate that rTMS can exert powerful protective and restorative effects on the peri-infarct microvasculature after PT stroke by, in part, promoting HIF-1α signaling and shifting vessel-associated astrocytic polarization to the A2 phenotype. This study provides further support for the potent protective effects of rTMS in the context of ischemic stroke, and these findings implicate vascular repair and protection as an important underlying phenomenon.