Traumatic brain injury (TBI) is one of the most frequent causes of mortality and disability worldwide, which has become a main public health concern [1]. As a result of the heterogeneous nature of TBI and often induces complex pathogenesis, the effective pharmacological treatments for TBI remain limited [2]. TBI is divided into primary injury and secondary injury. Primary injury occurs during an episode of TBI and is worsened by acute systemic complications such as hypotension and hypoxia. Subsequently, secondary injury results in activation of microglia and astrocytes, infiltration of leukocytes, and sustained secretion of inflammatory elements, ultimately leading to neuronal death [3,4]. Microglia cells are resident immune cells that trigger inflammation and immune responses. A growing number of evidences have revealed that microglia activation and neuroinflammation play an integral role in the pathophysiology of TBI [5,6]. However, the pathophysiological mechanisms and targeted pharmacological interventions for neuroinflammation in TBI are not yet fully understood. Thus, it is of great interest for us to search for promising therapeutic targets for TBI.

Hydrogen (H2), due to its selective antioxidant properties and cellular energy regulation, has become a safe and effective new therapeutic drug [7]. Prior researches have revealed that H2 may relieve organ damage and physiological barriers via suppressing oxidative stress, inhibiting inflammatory responses and modulating cellular autophagy [8]. Additionally, H2 has been shown to have latent neuroprotective effects in brain injury. For instance, H2 enhanced NEDD4-CX43-regulated mitochondrial autophagy to exert a protective effect against brain injury [9]. Wang et al. found that H2 exerted neuroprotective effects against neuronal apoptosis in TBI through activation of miR-21/PI3K/AKT/GSK-3β axis [10]. However, the protective effect of H2 on TBI needs to be further investigated.

Needle-embedding therapy, a non-pharmacological therapy of Chinese medicine, regulated the operation of meridians and stimulates the body's self-regulation function through continuous stimulation of acupuncture points [11]. Researches have demonstrated that needle-embedding therapy affected the neuroendocrine system and regulated the release of bioactive substances in the body to exert therapeutic effects [12]. In recent years, needle-embedding therapy has emerged as a promising therapeutic intervention for various neurological and pain disorders therapies [13]. However, no studies have been conducted on the effects of hydrogen combined with needle-embedding therapy on TBI.

Stimulator of interferon genes (STING) is a critical transmembrane dimeric protein located on the endoplasmic reticulum that upregulates type I interferon through activating interferon regulatory factor 3 (IRF3) and NF-κB signaling pathways [14]. In recent years, STING was evidenced to be involved in mediating inflammation and immune response in a variety of diseases. Report from Liao et al. suggested that HDAC3 inhibition ameliorated I/R-induced brain injury through cGAS-STING pathway [15]. Furthermore, Shi et al. revealed that NETs suppression with Cl-amidine improved neuroinflammation and neurological deficits through STING-dependent signaling pathway after TBI [16]. In addition, the STING signaling pathway promoted the NLRP3 inflammasome activation in immune cells, which consists of three main members, namely ASC, NLRP3, and procaspase-1 [17]. Activated NLRP3 inflammasome initiated inflammation via promoting the release of mature IL-1β and IL-18. Zhang et al. have confirmed that STING regulated neuroinflammatory response via activating NLRP3-related pyroptosis in TBI [18]. Nevertheless, whether hydrogen combined with needle-embedding therapy can be involved in alleviating neuroinflammation in TBI through regulating NLRP3 inflammasome and STING signaling pathway remain unclear.

In the present research, CCI-induced TBI mouse model was conduct to reveal the effect of hydrogen combined with needle-embedding therapy on TBI and explain the molecular mechanisms involved. Our observations may provide a novel therapeutic intervention for TBI.