Depression is one of the most important mental illnesses and is closely related to inflammation. Betaine is a natural product with an anti-inflammatory and antioxidant activities. However, the mechanism by which betaine ameliorates depression-like behaviors induced by lipopolysaccharide (LPS) is poorly understood. The purpose of this study was to investigate the neuroprotective effect of betaine on LPS-induced depression-like behavior in mice and its mechanism of action. ICR mice were randomly divided into four groups: the control group, the LPS model group (0.83mg/kg), the positive drug group (MIDO, 50mg/kg), and the betaine group (5 and 1 in drinking water). The betaine group was administered for 21 days, and on the 22nd day, except for the blank group, LPS (0.83mg/kg) was intraperitoneally injected to establish a lipopolysaccharide-induced mice depression-like model. Twenty-four hours after LPS injection, the tail suspension test (TST), open field test (OFT), and sucrose preference test (SPT) were performed to evaluate the effect of betaine on LPS-induced depressive behavior in mice. After the behavioral study, the mouse brain, hippocampus, and serum were taken for detection. The expressions of cytokines and inflammatory mediators were detected by ELISA, HE staining, immunofluorescence, immunohistochemistry, and western blotting. Western blotting was used to detect the protein expression levels of the nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), caspase-1, and ASC, the protein expression levels of the microglial polarization markers COX-2, inducible nitric oxide synthase (iNOS), and CD206. The results showed that betaine significantly ameliorated the depression-like behavior in LPS-induced mice, significantly attenuated the production of proinflammatory cytokines and increased the release of an anti-inflammatory cytokines. Betaine decreased the expression of the NLRP3 inflammasome, decreased the expression of M1 polarization markers, tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β), COX-2, and iNOS and promoted the expression of M2 polarization marker CD206. Our study suggests that betaine may promote the transition of microglia from the M1 to the M2 phenotype by inhibiting NLRP3 inflammasome activation, thereby attenuating lipopolysaccharide-induced depression-like behavior.

Background: Mental disorders among refugees have been well explored in several studies. However, longitudinal studies on the impact of the pandemic on refugee populations are widely lacking. This study was designed to examine the impact of the current pandemic on the mental health of Rohingya refugees living in Bangladesh. Method: This longitudinal study involved a convenience sample of 732 Rohingya people with pre-existing health problems who lived in the Kutupalong refugee camp in Cox’s Bazar, Bangladesh. The first recruitment was performed on 5 July 2019 (prepandemic visit) and assessed the health status of refugees using the Refugee Health Screener-15 (RHS-15). The follow-up survey was conducted on 10 November 2020, approximately 15 months later, during the pandemic. A total of 342 Rohingya refugees who completed the initial survey participated in the follow-up survey. A newly developed COVID-19 Impact on Quality of Life (COV19-QoL) scale was used alongside the RHS-15 scale during the second survey. Ethical measures were taken in compliance with the current Declaration of Helsinki. The analysis was performed using SPSS 26. Result: A total of 342 Rohingya refugees completed this longitudinal survey. The average age of participants was 32.25 ± 14.01 years (SD), and the predominant age group was ≤ 30 years (n = 207, 60.5%). Most of the participants were female (n = 209, 61.1%). A significant increase in stress was noted from the prepandemic to pandemic periods, as determined by the RHS-15 scale (RHS-15 Part I: 22.96 ± 8.43 vs. 46.72 ± 1.87, p < 0.001; and RHS-15 Part II: 4.43 ± 1.59 vs. 6.91 ± 1.49, p < 0.001). The mean COV19-QoL score of the participants was 4.47 ± 0.15 (out of 5), indicating a perceived negative impact of the pandemic in their lives. In the multiple regression analysis, female sex (β = 0.604, p = 0.017) and COV19-QoL score (β = 2.537, p = 0.003) were significantly associated with higher perceived distress among participants. Conclusion: Rohingya refugees experienced a significant deterioration of mental health during the COVID-19 pandemic. Alongside other socioeconomic, environmental, and political factors, the pandemic itself might have been a crucial contributor to this negative trend.