Gynostemma pentaphyllum is a herbal medicine widely used in Asian countries, and its saponin extracts have been shown to possess potent anti-inflammatory effects. Gypenoside XVII, an active ingredient isolated from Gynostemma pentaphyllum, has been found to alleviate the inflammation induced by LPS in the BV2 microglia, according to our preliminary study. This study aims to evaluate whether Gypenoside XVII could attenuate depression-like symptoms in vivo and tries to demonstrate the involvement of the complement regulation in its antidepressant-like effect. The results showed that Gypenoside XVII significantly attenuated depression-like behaviors in the forced swimming test, tail suspension test and sucrose preference test. It also alleviated the acute stress-induced hyperactivity of serum corticosterone levels. Additionally, Gypenoside XVII significantly inhibited the activation of microglia and the expression of C3 in mice exposed to chronic unpredictable mild stress (CUMS). Meanwhile, the activation of C3aR/STAT3 signaling and the expression of proinflammatory cytokines was reversed by Gypenoside XVII. Moreover, CUMS induced excessive synaptic pruning by activating microglia, while Gypenoside XVII restored it in the prefrontal cortex. Our data demonstrated that Gypenoside XVII, the active ingredient of Gynostemma pentaphyllum, produced the antidepressant-like effects in mice, which was mediated by the inhibition of complement C3/C3aR/STAT3/cytokine signaling in the prefrontal cortex.

Microglia respond to stressors by secreting cytokines or growth factors, playing a crucial role in maintaining brain homeostasis. While the antidepressant-like effects of Polygonatum sibiricum polysaccharides (PSPs) have been observed in mice, their potential effectiveness involving microglial regulation remains unknown. This study investigates the antidepressant-like mechanism of PSP by regulating microglial phenotype and signaling pathways in the prefrontal cortex of chronic restraint stress (CRS)-induced mice. PSP was extracted, purified, characterized, and orally administered to CRS mice. High-performance gel permeation chromatography (HPGPC) revealed that PSP has a molecular weight of 5.6 kDa. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed that PSP exhibited a layered structure with densely packed, irregular surfaces. PSP treatment significantly increased sucrose preference (low: 71%, p < 0.01; medium: 69%, p < 0.05; high: 75%, p < 0.001 vs. CRS: 58%) and reduced immobility time (low: 74 s, p < 0.01; medium: 68 s, p < 0.01; high: 79 s, p < 0.05 vs. CRS: 129 s), indicating the alleviation of depressive-like behaviors. PSP inhibited microglial activation (PSP, 131/mm² vs. CRS, 173/mm², p = 0.057), reversing CRS-induced microglial hypertrophy and hyper-ramification. Furthermore, PSP inactivated microglial activation by inhibiting NLRP3/ASC/caspase-1/IL-1β signaling pathways, increasing BDNF synthesis and activating brain-derived neurotrophic factor (BDNF)-mediated neurogenesis (PSP, 80/per DG vs. CRS, 49/per DG, p < 0.01). In conclusion, PSP exerts antidepressant-like effects through the regulation of microglial activity and neuroinflammatory pathways, indicating it as a potential natural compound for depression treatment.

In this work, we have developed a simple and rapid colorimetric assay for the detection of immunoglobulin E (IgE) using functional nucleic acids (FNAs) and a solid-phase competition enzyme-linked immunosorbent assay (ELISA). The FNAs including aptamer of recombinant IgE, G-quadruplex and its complementary fragments were immobilized on 96-well microplates to achieve recognition and detection of IgE in biological samples. The G-quadruplex DNAzyme catalyzed 2,2′-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS)-hemin-H₂O₂ system was used to improve the sensitivity of colorimetric assay. In the presence of IgE, the hairpin structure and G-quadruplex would be destroyed, resulting in the inactivation of DNAzyme and subsequent reduction of its absorbance. This cost-effective approach detected IgE in the linear range from 5.0 pg/mL to 500 ng/mL, with the limit of detection (LOD) of 2.0 pg/mL, under optimal conditions. Moreover, the developed method was successfully applied to the rapid detection of IgE in human urine, indicating a great potentiality of this approach in clinical diagnosis and other biomedical applications.