The protein expressions of neurotrophic factors can be enhanced by low-intensity pulsed ultrasound (LIPUS) stimulation in the brain. The purpose of this study was to demonstrate the protective effect of LIPUS stimulation against aluminum-induced cerebral damage in Alzheimer's disease rat model. LIPUS was administered 7 days before each aluminum chloride (AlCl₃) administration and concomitantly given with AlCl₃ daily for a period of 6 weeks. Neurotrophic factors in hippocampus were measured by western blot analysis. Behavioral changes in the Morris water maze and elevated plus maze were examined in rats after administration of AlCl₃. Various biochemical analyses were performed to evaluate the extent of brain damages. LIPUS is capable of prompting levels of brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF) and vascular endothelial growth factor (VEGF) in rat brain. AlCl₃ administration resulted in a significant increase in the aluminum concentration, acetylcholinesterase activity and beta-amyloid (Aβ) deposition in AlCl₃ treated rats. LIPUS stimulation significantly attenuated aluminum concentration, acetylcholinesterase activity, Aβ deposition and karyopyknosis in AlCl₃ treated rats. Furthermore, LIPUS significantly improved memory retention in AlCl₃-induced memory impairment. These experimental results indicate that LIPUS has neuroprotective effects against AlCl₃-induced cerebral damages and cognitive dysfunction.

Introduction: Activated microglia can be polarized to the pro‐inflammatory M1 phenotype and the anti‐inflammatory M2 phenotype. Low‐intensity pulsed ultrasound (LIPUS) can attenuate pro‐inflammatory responses in activated microglia.Objective: This study aimed to investigate the effects of LIPUS on M1/M2 polarization of microglial cells and the regulatory mechanisms associated with signaling pathways.Methods: BV‐2 microglial cells were stimulated by lipopolysaccharide (LPS) to an M1 phenotype or by interleukin‐4 (IL‐4) to an M2 phenotype. Some microglial cells were exposed to LIPUS, while others were not. M1/M2 marker mRNA and protein expression were measured using real‐time polymerase chain reaction and western blot, respectively. Immunofluorescence staining was performed to determine inducible nitric oxide synthase (iNOS)‐/arginase‐1 (Arg‐1)‐ and CD68‐/CD206‐positive cells.Results: LIPUS treatment significantly attenuated LPS‐induced increases in inflammatory markers (iNOS, tumor necrosis factor‐α, interleukin‐1β, and interleukin‐6) as well as the expression of cell surface markers (CD86 and CD68) of M1‐polarized microglia. In contrast, LIPUS treatment significantly enhanced the expression of M2‐related markers (Arg‐1, IL‐10, and Ym1) and membrane protein (CD206). LIPUS treatment prevented M1 polarization of microglia and enhanced or sustained M2 polarization by regulating M1/M2 polarization through the signal transducer and activator of transcription 1/STAT6/peroxisome proliferator‐activated receptor gamma pathways.Conclusions: Our findings suggest that LIPUS inhibits microglial polarization and switches microglia from the M1 to the M2 phenotype.

Low-intensity pulsed ultrasound (LIPUS) stimulation has been shown to increase the expression of brain-derived neurotrophic factor (BDNF) in astrocytes of an in vitro model and rat brains of an in vivo model; however, their molecular mechanisms are still not well clarified. Here, we investigated the underlying mechanisms of BDNF enhancement by LIPUS in rat cerebral cortex astrocytes. After LIPUS stimulation in astrocytes, the protein and mRNA expressions were measured by western blot and RT–PCR, respectively. The concentration of intracellular calcium was determined spectrophotometrically. The results showed that LIPUS enhanced the phosphorylation of tropomyosin-related kinase B (TrkB) and Akt but had no effect on Erk1/2 phosphorylation. Additionally, LIPUS increased the intracellular concentration of calcium and enhanced the protein levels of calmodulin-dependent kinase (CaMK) II and CaMKIV. LIPUS also activated the phosphorylation of NF-κB-p65 but did not promote the activation of cAMP response element-binding protein (CREB). Taken together, our results suggest that LIPUS stimulation upregulates BDNF production in astrocytes through the activation of NF-κB via the TrkB/PI3K/Akt and calcium/CaMK signaling pathways. BDNF has emerged as a major molecular player in the regulation of neural circuit development and function. Therefore, LIPUS stimulation may play a crucial and beneficial role in neurodegenerative diseases.

The purpose of this study was to investigate the restorative role of low-intensity pulsed ultrasound (LIPUS) against lipopolysaccharide (LPS)-induced neuroinflammation and memory impairments in a simulation of Alzheimer’s disease. Mice subjected to LPS administration (250 μg/kg, i.p.) were treated with LIPUS daily for 7 days. The levels of brain-derived neurotrophic factor (BDNF) and inflammatory markers were estimated in brain tissue using western blot. After LIPUS treatment, the neuroprotective effects of LIPUS in mice were assessed by behavioral tests. LPS plus LIPUS-treated mice exhibited a significant increase in the average time spent in the target quadrant compared to the LPS-treated group. Compared with the LPS-treated group, LPS plus LIPUS-treated mice revealed a preference for the novel object. LIPUS treatment significantly attenuated LPS-induced increases in the expression of amyloid-beta (Aβ) and amyloid precursor protein (APP) in the hippocampus region of LPS-treated mice. Furthermore, LIPUS significantly reduced the protein levels of TNF-α, IL-1β, and IL-6 in the mice brain induced by LPS. LIPUS treatment induces neuroprotection by inhibiting the LPS-induced activation of TLR4/NF-κB inflammatory signaling and by enhancing the associated CREB/BDNF expression in LPS-treated mice. Our data showed that LIPUS attenuated LPS-induced memory impairment as well as amyloidogenesis via the suppression of neuroinflammatory activity and BDNF decline.