1. Introduction
lzheimer Disease (AD) is a progressive neurodegenerative disease caused by the deposition of amyloid plaques and neurofibrillary tangles in the brain [1]. β-Amyloid protein is the most abundant protein compound in neurotic plaques [2]. However, microglial cells enhance phagocytosis and amyloid plaque degradation in the nervous system [3]. There is evidence that magnetic fields can cause AD and other neurological conditions in humans [4, 5]. It has been reported that the effects of magnetic fields can vary depending on the physical characteristics of the field (electric, magnetic, or electromagnetic), the frequency (low, medium, high), the wave oscillation (pulsed or constant waves), and the duration of exposure [6]. On the other hand, other studies have shown the positive effects of magnetic fields, such as a decrease in inflammation, increased differentiation of stem cells into neurons, the proliferation of glial cells, and synaptic plasticity in the dentate gyrus [7]. This study aimed to assess β-amyloid deposition and microglia amount in the brains of male rats that had been treated with magnetic fields before and after the AD model induction.
2. Methods  
This experimental study was performed at Hamadan University of Medical Sciences’ Embryology Lab and Neurophysiological Research Center, Hamadan City, Iran. The rats were divided into five groups at random. First, the control group was not exposed to magnetic fields or amyloid injections.  Second, the magnetic field group (Extremely Low-Frequency Magnetic Fields [ELF-EMF]) was exposed to the magnetic field without β-amyloid. Third, the AD group, which underwent stereotaxic surgery and received β-amyloid, but were not exposed to the magnetic field. Fourth, the treatment model before AD. They underwent magnetic field one week before surgery and β-amyloid injection and were treated for two months after surgery “AD + EMFs before AD”.  Fifth, the treatment group after AD model “AD + EMFs after AD”. They were treated with a magnetic field for two months after surgery and β-amyloid injection. Following tissue preparation and immunohistochemistry techniques, β-amyloid and allograft inflammatory factor 1  (Iba1) were assessed. Microglial cells were observed directly using fluorescent microscopy and ImageJ software [8]. Data were analyzed by 1-way ANOVA and tukey post hoc test in SPSS v. 16. The significance level was considered as P<0.001.
3. Results
Compared to the AD group that received β-amyloid injection alone, the amount of β-amyloid protein was significantly reduced in the “AD + EMFs before AD” and “AD + EMFs after AD” groups, indicating that the magnetic field reduces β-amyloid deposition. There were no significant differences between the “AD + EMFs before AD” and “AD + EMFs after AD” groups. Immunohistochemical analysis also revealed a significant increase in microglial cells in both study groups using antibodies against Iba1. Moreover, microglial cell count increased significantly in two months in the “AD + EMFs before AD” and “AD + EMFs after AD” groups compared to the AD group. Still, there was no difference between the “AD + EMFs before AD” and “AD + EMFs after AD” groups.
4. Discussion and Conclusion
The results revealed that electromagnetic fields significantly reduced β-amyloid plaques. In other words, it played a positive role in treating AD. In addition, another study by Auxiliary et al. showed that exposure to a magnetic field would induce incremental and long-term synaptic enhancement [9]. Also consistent with the present study results, Liotti et al. showed an increase in memory and learning following exposure to a magnetic field after 4 weeks of exposure to a 50-Hz magnetic field for 1 or 4 hours. They reported for the first time that chronic exposure to a magnetic field has a positive effect on the acquisition and maintenance of spatial memory [10]. In addition, the results of Ji et al. study showed that long-term RF-EMF exposure has beneficial effects on reducing β-amyloid deposition, which confirms our results [11].
According to the present study, the number of microglial cells increased in the AD group, and that increase was greater in the “AD + EMFs before AD” and “AD + EMFs after AD” groups. EMFs could reduce some of the most well-known proinflammatory cytokines, such as Tumor Necrosis Factor (TNF)-α, interleukin (IL)-1β, and IL-6 in N9 microglia. These data suggest that EMFs have an anti-inflammatory effect on microglial cells and protect neurons from hypoxic damage [12]. This finding indicates that EMFs may be used to treat cerebral ischemia. One study reports that ELF-EMF (50 Hz, 1 mT) inhibits the nuclear factor kappa B signaling pathway for regulating chemokine production and glial cell growth and preventing inflammation [13]. Gao et al. found that ELF-EMF could activate the Notch signaling pathway [7]. They discovered that neural stem cells proliferation and differentiation in cerebral ischemia are closely related to the Notch pathway [14]. This event is associated with increased synaptic plasticity in the dentate gyrus [7]. Also, consistent with our study, the results of Duong et al. study showed that EMF has a positive effect on the survival of microglial cells [15]. Based on the study results, magnetic waves can reduce the formation of β-amyloid plaques and treat AD, but they cannot prevent it. Waves can also activate microglia and increase their activity. In conclusion, magnetic waves may be used to eliminate β-amyloid plaques and treat AD.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Ethics Committee of the Hamadan University of Medical Sciences (Code: IR.UMSHA.REC.1396.17).

Funding
This study was supported by the Hamadan University of Medical Sciences’ Embryology Lab and Neurophysiological Research Center.

Authors' contributions
Conceptualization, visualization, project administration, and resources, methodology, editing, review, investigation, and supervision, original draft preparation: All authors; Data collection and formal analysis: Zoleikha Golipoor.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
The authors would like to thank the Vice-Chancellor for Hamadan University of Medical Sciences for the support and cooperation.


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