Effect of static pressure on ultrasonic liquid phase exfoliation of few-layer graphene.

Ultrasonic Liquid Phase Exfoliation (LPE) has gathered attention from both scientific and industrial communities for its accessibility and cost-effectiveness in producing graphene. However, this technique has faced challenges such as low yield and long production time. In this study, we developed a cyclic ultrasonication system to exfoliate expanded graphite (EG) by applying static pressure to a flow chamber to address these challenges. Using deionized water (DIW) as solvent and polyvinylpyrrolidone (PVP) as dispersion, we obtained graphene slurries with an average lateral size of 7 µm and averaged number of layers of 3.5 layers, after 40 min of ultrasonication. After centrifugation, the yield of single and bilayer graphene was approximately 16 %. The findings showed that regulating hydrostatic pressure can effectively affect the lateral size and number of layers of few-layer graphene. The proposed method is of good potential for scaled-up production of few-layer graphene.

Diversity, Distribution, and Biogeography of Freshwater Fishes in Guangxi, China.

The Guangxi Zhuang Autonomous Region has the largest number of cavefish species in the world and is a global biodiversity hotspot. In this study, a species list of freshwater fishes in 12 Sub-basins of Guangxi was compiled systematically. Moreover, the species composition and distribution of the diversity were analyzed via the G-F index, taxonomic diversity index, and beta diversity index. Results showed that 380 species of freshwater fishes were recorded in this region, which belonged to 158 genera in 43 families and 17 orders in 2 phyla, in which 128 species of endemic fishes and 83 species of cavefish accounted for 33.68% and 21.84%, respectively. The species diversity from northwest to southeast gradually decreased for most Sub-basins. The G-F index has generally risen in recent years. The taxonomic diversity index showed that the freshwater fish taxonomic composition in Guangxi is uneven. The spatial turnover component was the main contributor to beta diversity. A cluster analysis showed that the 12 Sub-basins in the study area could be divided into four groups, and the phylogenetic relationships of freshwater fishes in Guangxi generally reflect the connections between water systems and geological history. The freshwater fish system in Guangxi, which belonged to the South China division in the Southeast Asiatic subregion of the Oriental region, originated in the early Tertiary period. The results will provide the information needed for freshwater fish resource protection in Guangxi and a reference for promoting the normalization of fish diversity conservation in the Pearl River Basin and other basins.

Antidepressive properties of microglial stimulation in a mouse model of depression induced by chronic unpredictable stress.

The decrease of microglia in the hippocampus is a novel mechanism for depression onset. Reversal of this decrease can ameliorate stress-induced depression-like behaviors in rodents. However, the property of this therapeutic strategy remains unclear. We addressed this issue by designing a series of behavioral experiments. Results showed that a single lipopolysaccharide (LPS) injection at the dose of 75 and 100 µg/kg, but not at 30 or 50 µg/kg, produced obvious antidepressant effects in chronic unpredictable stress (CUS) mice at 5 h after the drug administration. In the time-dependent experiment, a single LPS injection (100 µg/kg) ameliorated the CUS-induced depression-like behaviors in mice at 5 and 8 h, but not at 3 h, after the drug administration. The antidepressant effect of a single LPS injection persisted at least 10 days and disappeared at 14 days after the drug administration. 14 days after the first injection, a second LPS injection (100 µg/kg) still produced antidepressant effects in chronically-stressed mice who re-displayed depression-like behaviors at 5 h after the drug administration. The antidepressant effect of LPS appears to be dependent on microglia, as at 5 h after LPS administration (100 µg/kg), the CUS-induced decrease in microglial numbers and Iba-1 mRNA levels in the hippocampus was reversed markedly, and inhibition of microglia by minocycline (40 mg/kg) or PLX33297 (290 mg/kg) prevented the antidepressant effect of LPS in CUS mice. These results indicate that a single LPS injection displays rapid and sustained antidepressant effects in chronically stressed mice likely through stimulating hippocampal microglia.

Identification of a microglial activation-dependent antidepressant effect of amphotericin B liposome.

Chronic stress-induced decline in microglia in the hippocampus is a newly hypothesized mechanism of depression, and reversal of this decline by microglial activators has been shown to suppress depression-like behaviors in mice. This suggests that activation of immune cells in the hippocampus may be a potential strategy for depression therapy. Since amphotericin B, an anti-fungal medication, is known to activate macrophages and microglia, we investigated whether conventional amphotericin B or its liposomal form displays antidepressant activity. Our results showed that both amphotericin B and its liposomal form at various doses induced obvious depression-like behaviors in naïve mice, likely owing to increased serum interleukin-6 (IL-6) and IL-1ß levels. However, under stressed conditions, amphotericin B liposome, but not amphotericin B itself, reversed chronic unpredictable stress (CUS)-induced increase in immobility time in the tail suspension test and forced swim test as well as CUS-induced decrease in sucrose intake in the sucrose preference test and the time spent in the center region of the open field test in a dose-dependent manner. Immunofluorescence analysis showed that amphotericin B liposome reversed the CUS-induced decline in dentate gyrus (DG) microglia, and inhibition or ablation of microglia in the hippocampus by minocycline (40 mg/kg) or PLX3397 pre-treatment (290 mg/kg) abrogated the antidepressant effect of the amphotericin B liposome in CUS-treated mice. These results not only identify a novel pharmacological effect of amphotericin B liposome, but further support the notion that microglial activation in the hippocampus is a potential strategy for depression therapy.

Sulforaphane triggers a functional elongation of microglial process via the Akt signal.

Microglia are a kind of innate immune cells in the nervous system. The amoeboid morphology in microglia indicates a pro-inflammatory status, while their ramified morphologies are associated with anti-neuroinflammation. Recently, we and others have reported that drugs that trigger microglial process elongation may be beneficial for neuroinflammation inhibition. In this study, we found that sulforaphane (SFN), a compound extracted from broccoli sprouts, promotes primary cultured microglial process elongation in both normal and pro-inflammatory conditions in a reversible manner. This pro-elongation effect of SFN was also observed in the prefrontal cortex in vivo and accompanied with an attenuation of pro-inflammatory response as well as an enhancement of anti-inflammatory response in primary cultured microglia. Mechanistic studies revealed that the SFN treatment increased Akt phosphorylation levels in primary cultured microglia and Akt inhibition blocked the effect of SFN on microglial process elongation, suggesting that the regulation of microglial process by SFN is mediated by Akt activation. Functional studies showed that Akt inhibition reversed the effect of SFN on both pro- and anti-inflammatory responses in lipopolysaccharide (LPS)-stimulated microglia. In an inflammation model in vivo, SFN pretreatment not only prevented LPS-induced retractions of microglial process in the prefrontal cortex, but improved LPS-induced behavioral abnormalities in mice, including the increase in immobility time in the tail suspension test and forced swim test as well as the decrease in sucrose preference. These results indicate that the SFN inhibits microglial activation and neuroinflammation-triggered behavioral abnormalities likely through triggering Akt-mediated microglial process elongation.

SMIP004: A compound with antidepressant-like activities in mouse models.

This study was designed to examine the potency of SMIP004, an inhibitor of S-phase kinase-associated protein 2 (Skp2), to exert antidepressant-like properties in mouse models following acute or chronic administration to C57BL6/J mice. To this end, the tail suspension test (TST), forced swim test (FST), and sucrose preference test (SPT) were utilized and the antidepressant-like activity of SMIP004 at different concentrations or time points in mice with or without chronic unpredictable stress (CUS) treatment were evaluated. Results showed that in the time- and dose-dependent experiment the antidepressant-like activity of SMIP004 in naïve mice occurred at day 11 and at the dosage of 2 and 4 mg/kg. SMIP004 (2 mg/kg) also produces antidepressant-like activities in naïve mice after three times in a 24-h administration scheme (24, 5, and 1 h before the test) but not after acute treatment (1 h before the test). Combined SMIP004-fluoxetine administration was found to induce coordinated antidepressant-like effects in naïve mice in the TST and FST. These results seem to be specific because the mice in different experimental groups showed no increased locomotor activity in the open field test. Further, long-term SMIP004 treatment at the dosage of 2 but not 1 mg/kg reversed CUS-induced increase in immobility time in the TST and FST as well as CUS-induced decrease in sucrose preference in the SPT, suggesting that SMIP004 can produce antidepressant-like activities at stressed conditions. These results show that SMIP004 displays obvious antidepressant-like activities in all conducted tests, and suggest that SMIP004 might be a novel antidepressant.

Tauroursodeoxycholic acid produces antidepressant-like effects in a chronic unpredictable stress model of depression via attenuation of neuroinflammation, oxido-nitrosative stress, and endoplasmic reticulum stress.

Depression is a common psychiatric disorder with heavy economic and social burdens. Searching new agents with better antidepressant-like activities is of great significance for depression therapy. Tauroursodeoxycholic acid (TUDCA), a clinical drug for gallstone treatment, possesses neuroprotective effects in different brain disorders. However, whether it affects depression remains unclear. We addressed this issue by evaluating the effect of TUDCA on depression induced by chronic unpredictable stress (CUS). Results showed that TUDCA treatment at 200 but not 100 mg/kg prevented the 5 weeks of CUS-induced increases in the immobile time of C57BL6/J mice in the experiments of forced swimming test and tail suspension test as well as the CUS-induced decrease in sucrose intake and crossing numbers in the open-field test, and did not enhance the antidepressant-like effect of fluoxetine. Attenuation of neuroinflammation may be involved in the antidepressant-like effect of TUDCA, as TUDCA treatment (200 mg/kg) normalized the levels of tumor necrosis factor-α and interleukin-6 in both hippocampus and prefrontal cortex. The increases in inflammasome and microglial activation markers, including interleukin-ß, nod-like receptor protein 3, and Iba-1, in CUS-treated mice were reduced by TUDCA treatment (200 mg/kg). TUDCA treatment (200 mg/kg) also normalized the changes in markers reflecting the oxidative-nitrosative and endoplasmic reticulum (ER) stress induced by CUS, such as nitric oxide, reduced glutathione, malondialdehyde, glucose-regulated protein 78, and C/EBP homologous protein. These results revealed that TUDCA improved the CUS-induced depression-like behaviors likely through attenuation of neuroinflammation, oxido-nitrosative, and ER stress.

Dynamic changes in hippocampal microglia contribute to depressive-like behavior induced by early social isolation.

Depression triggered by early-life stress has begun to attract wide attention due to its severe symptoms and poor treatment outcomes. However, the pathophysiological mechanism for this type of depression remains unclear. Recently, we and others reported that different types of chronic stress induce a significant loss of hippocampal microglia, which is mediated by an initial activation of these microglia. Since early-life stress also promotes microglial activation, we investigated the dynamic changes in hippocampal microglia in mice suffering from depression induced by early social isolation (ESI). Results showed that 8 days of ESI induced depressive-like behaviors in a tail suspension test, forced swim test, sucrose preference test, and open field test, and it also induced a loss and dystrophy of hippocampal microglia. We found that this ESI-induced loss of hippocampal microglia was mediated by both microglial activation and apoptosis. This was demonstrated by the following results: (i) 1 day of ESI induced an obvious activation of hippocampal microglia followed by their apoptosis, and (ii) the blockade of the initial activation of hippocampal microglia by minocycline pretreatment suppressed the ESI-induced apoptosis and loss as well as ESI-induced depressive-like behavior. Lipopolysaccharide (LPS) and macrophage colony-stimulating factor (M-CSF), two activators of microglia, almost completely reversed ESI-induced depressive-like behavior by promoting microglial proliferation in the hippocampus. These results reveal an etiological role of hippocampal microglial loss in ESI-induced depression and demonstrate that the restoration of microglial homeostasis in the hippocampus may serve as a therapeutic strategy for depression induced by early-life stress.

Sodium butyrate triggers a functional elongation of microglial process via Akt-small RhoGTPase activation and HDACs inhibition.

Microglia, a type of immune cell in the brain, are in a ramified status with branched processes in normal conditions. Upon pathological stimulation, microglia retract their processes and become activated. Searching methods to make the activated microglia return to ramified status would help cope with injuries induced by neuroinflammation. Here, we investigated the influence of sodium butyrate (SB), a sodium salt form of butyrate produced by fermentation of dietary fibers in the gut on microglial process. Results showed that SB induced reversible elongations of microglial process in both normal and inflammatory conditions, and these elongations were accompanied with significant changes in markers reflecting the pro-inflammatory and anti-inflammatory status of microglia. The protein kinase B (Akt)-RhoGTPase signal was considered to mediate the effect of SB on microglial process, as: i) SB activated the small RhoGTPases Rac1 and Cdc42; ii) SB promotes Akt phosphorylation; iii) Rac1, Cdc42, and Akt inhibition abrogated the pro-elongation effect of SB on microglial process. Further analysis showed that incubation of microglia with two other histone deacetylases (HDACs) inhibitors trichostatin A (TSA) and valproic acid (VPA) also promoted microglial process elongation and Akt phosphorylation, suggesting that the SB-triggered microglial process elongation may be mediated by HDACs inhibition. Furthermore, Akt inhibition prevented the anti-inflammatory effect of SB in primary cultured microglia, and abrogated the inhibitory effects of SB on microglial process retraction and behavioral abnormalities induced by lipopolysaccharide (LPS). These results for the first time identify an anti-inflammatory role of SB from the aspect of microglial process elongation.

The ketone body metabolite ß-hydroxybutyrate induces an antidepression-associated ramification of microglia via HDACs inhibition-triggered Akt-small RhoGTPase activation.

Direct induction of macrophage ramification has been shown to promote an alternative (M2) polarization, suggesting that the ramified morphology may determine the function of immune cells. The ketone body metabolite ß-hydroxybutyrate (BHB) elevated in conditions including fasting and low-carbohydrate ketogenic diet (KD) can reduce neuroinflammation. However, how exactly BHB impacts microglia remains unclear. We report that BHB as well as its producing stimuli fasting and KD induced obvious ramifications of murine microglia in basal and inflammatory conditions in a reversible manner, and these ramifications were accompanied with microglial profile toward M2 polarization and phagocytosis. The protein kinase B (Akt)-small RhoGTPase axis was found to mediate the effect of BHB on microglial shape change, as (i) BHB activated the microglial small RhoGTPase (Rac1, Cdc42) and Akt; (ii) Akt and Rac1-Cdc42 inhibition abolished the pro-ramification effect of BHB; (iii) Akt inhibition prevented the activation of Rac1-Cdc42 induced by BHB treatment. Incubation of microglia with other classical histone deacetylases (HDACs) inhibitors, but not G protein-coupled receptor 109a (GPR109a) activators, also induced microglial ramification and Akt activation, suggesting that the BHB-induced ramification of microglia may be triggered by HDACs inhibition. Functionally, Akt inhibition was found to abrogate the effects of BHB on microglial polarization and phagocytosis. In neuroinflammatory models induced by lipopolysaccharide (LPS) or chronic unpredictable stress (CUS), BHB prevented the microglial process retraction and depressive-like behaviors, and these effects were abolished by Akt inhibition. Our findings for the first time showed that BHB exerts anti-inflammatory actions via promotion of microglial ramification.