As a traditional tonic Chinese herb, ginseng plays a vital role in the national medicine systems of China, Japan, South Korea, and other countries [1]. Its multiple pharmacological activities—including enhancing immune function, counteracting oxidative stress, and improving neurological function—have been widely confirmed. GRg1 is an abundant triterpenoid active component in ginseng. It exerts effects such as alleviating stress responses by inhibiting the overactivation of the hypothalamic-pituitary-adrenal (HPA) axis, reducing neuroinflammation by blocking the activation of the NLRP3 inflammasome, and improving energy metabolism disorders by regulating mitochondrial homeostasis [2], [3], [4], [5], [6]. These studies provide important theoretical support for in-depth exploration of its antidepressant molecular mechanisms. Our previous research [3], [6] has revealed that GRg1 can reduce astrocyte-mediated neuroinflammatory responses and improve chronic stress-induced depressive-like behaviors by increasing the expression of Cx43. However, the specific molecular pathway through which GRg1 exerts antidepressant effects via Cx43 remains unclear.

Connexin 43 (Cx43) is a connexin with relatively high content in the CNS, and its expression is mainly localized in astrocytes. This protein consists of 382 amino acid residues with a molecular weight of approximately 43 kilodaltons (kDa) [7]. Existing studies have confirmed that Cx43 can exert a protective effect on embryonic cells by inhibiting ROS-induced autophagy and apoptosis processes, while maintaining the homeostasis of mitochondrial membrane potential(ΔΨm) [8]. In addition, rTMS can restore hindlimb motor function in spinal cord injury model mice by regulating the Cx43-mediated autophagic pathway [9]. Notably, the Cx43-mediated mitophagy process in astrocytes can effectively alleviate brain tissue damage induced by traumatic brain injury and exert a significant neuroprotective effect [10]. However, whether Cx43 can alleviate neuroinflammation and further improve depression-like behaviors by regulating the mitophagy still lacks direct experimental evidence, which is exactly the core starting point and main purpose of this study.

The pathogenesis of depression is closely associated with the activation of central neuroinflammation, with glial cell dysfunction as the core mediating link [11], [12]. During neuroinflammation, microglia serve as the primary source of key pro-inflammatory cytokines such as TNF-α [13], [14]. Although astrocytes are not the dominant secretors of pro-inflammatory cytokines, they can be induced by inflammatory signals released by microglia to transform into an A1 reactive phenotype, amplifying the inflammatory response [12], [15]. Meanwhile, astrocytes participate in the formation of depressive phenotypes by regulating the blood-brain barrier and synaptic plasticity [15], [16], [17], together forming a positive inflammatory feedback loop characterized by “microglia-initiated and astrocyte-amplified” inflammation. In animal models of depression, astrocytes exhibit both morphological damage (e.g., reduced branching and shortened processes) and excessive inflammatory activation: they produce large amounts of oxidative stress substances [18], [19], [20] and release pro-inflammatory cytokines such as IL-1β and IL-18 [21]. These substances act not only as “effector molecules” of neuroinflammation (directly damaging nerve cells) but also as “inducer molecules” that exacerbate the inflammatory response. Given that the mechanism by which “restoring astrocyte function interferes with the glial inflammatory synergistic loop” remains unclear, this study focuses on Cx43-mediated astrocyte inflammation to explore the role and mechanism of GRg1 in regulating astrocytes and intervening in the neuroinflammation-depression axis, thereby providing a theoretical basis for the treatment of depression.

Pyroptosis is a form of inflammatory cell death tightly regulated by genes, in which Gasdermin D (GSDMD) serves as the core effector molecule mediating pyroptosis. First, excessive reactive oxygen species (ROS) promote the formation of the inflammasome complex (NLRP3-ASC-Caspase-1) [22], [23]. Subsequently, the activated Caspase-1 specifically cleaves the full-length GSDMD protein, releasing the GSDMD amino-terminal fragment (GSDMD-N) with membrane-piercing activity [24], [25], [26]. GSDMD-N rapidly translocates to the cell membrane and forms pores on the membrane. This further leads to the leakage of cellular contents (e.g., IL-1β and IL-18), and simultaneously triggers cellular osmotic imbalance, thereby causing cell swelling and rupture [25], [27]. Since excessive accumulation of ROS can damage astrocytes, astrocytes have developed a series of mitochondrial protective mechanisms (e.g., mitophagy) during long-term evolution. These mechanisms promptly clear damaged mitochondria, reduce ROS production, and maintain mitochondrial homeostasis as well as cell survival. Dysregulation of this protective mechanism is considered a key inducer of astrocyte pyroptosis activation and the exacerbation of neuroinflammation. In the state of depression, abnormal mitophagy prevents the timely clearance of damaged mitochondria, thereby triggering a vicious cycle of oxidative stress and neuroinflammation [27], [28], [29]. Under normal physiological conditions, the mitophagy can promptly clear damaged mitochondria and reduce the release of ROS, thereby inhibiting pyroptosis and alleviating neuroinflammation. Conversely, when the mitophagy is impaired (abnormal expression of the PINK1/Parkin), a large number of damaged mitochondria accumulate within the cells. These damaged mitochondria continuously produce and ROS, thereby causing the cells to pyroptosis [19], [27], [30], [31]. This not only directly exacerbated oxidative stress damage, but also acted as an “inflammation trigger”, activating astrocytes and prompting the secretion of pro-inflammatory factors such as IL-1β and IL-18 [19], [27], [30]. This further confirms that targeted restoration of mitophagy may become an important strategy for anti-inflammatory treatment of depression.

Based on the above research background and scientific questions, we propose the core research hypothesis: GRg1 upregulates the expression of Cx43 in astrocytes, restores mitophagy function, reduces the abnormal release of ROS, thereby inhibiting astrocyte pyroptosis and neuroinflammatory responses, and ultimately improving depressive-like behaviors.