TAK1 Inhibition Attenuates Neuroinf lammation via Stabilization of Immune Negative Regulator TIPE2 in Microglial Models

摘要

Objective: Neurological disorders, encompassing Alzheimer's disease(AD), Parkinson's disease(PD), stroke, epilepsy, among others, represent a major public health challenge. These conditions are frequently accompanied by neurological dysfunctions that manifest as depression, anxiety, and chronic stress. Such abnormalities can induce neuroendocrine disturbances, which in turn compromise the integrity of the immune system. Additionally, dysregulated neuroimmune interactions have been implicated in the pathogenesis of neuropathic pain, metabolic syndrome, and a range of other human diseases. Accumulating evidence underscores the pivotal role of neuroinflammation—primarily driven by microglial activation—in the progression of numerous neurological disorders. Sustained microglial activation promotes the secretion of pro-inflammatory and cytotoxic mediators, leading to impaired neuronal function and establishing a deleterious feedback cycle between chronic neuroinflammation and neuronal damage. This cycle ultimately accelerates the advancement of disease pathology. Therefore, the modulation of microglia-driven neuroinflammatory responses represents a critical therapeutic strategy. With increasing evidence from recent studies, immune negative regulators have garnered significant attention for their role in controlling neuroinflammation. Among these, tumor necrosis factor-α-induced protein 8-like 2(TIPE2) has emerged as a key molecule that confers neuroprotection by mitigating inflammatory damage. Since specific pharmacological agents targeting TIPE2—such as agonists or inhibitors—remain unavailable, current research has shifted toward upstream regulatory mechanisms. It has been demonstrated that inhibition of transforming growth factor-β-activated kinase 1(TAK1) reduces ubiquitin-mediated degradation of TIPE2, leading to its stabilization and upregulated expression. This enhancement of TIPE2 function contributes to the suppression of neuroinflammatory pathways and promotes the restoration of immune homeostasis. Thus, targeting TAK1 presents a promising therapeutic avenue for attenuating neuroinflammation in neurological disorders. Methods: In vitro, an inflammatory injury model was established by stimulating BV2 microglial cells with lipopolysaccharide(LPS), with the aim of validating the regulatory role of TIPE2 in inflammation-associated signaling pathways. Protein expression levels of key markers including TAK1, TIPE2, interleukin-1β(IL-1β), and inducible nitric oxide synthase(i NOS) were assessed by western blot analysis. Additionally, quantitative realtime polymerase chain reaction(RT-q PCR) was performed to evaluate changes in m RNA expression of TIPE2, IL-1β, and other relevant molecular components. Results: Stimulation of BV2 cells with 1 μg/m L LPS successfully established an inflammatory injury model without compromising cell viability, while effectively inducing a robust inflammatory response, as evidenced by significant upregulation of key protein markers including IL-1β and i NOS. Following LPS challenge, a marked increase in TIPE2 m RNA expression was observed; however, TIPE2 protein levels were notably reduced, suggesting post-transcriptional regulation likely involving rapid protein degradation. Pretreatment with the TAK1 inhibitor 5Z-7-oxozeaenol prior to LPS stimulation effectively suppressed the activation of TAK1 and its downstream signaling molecules. This inhibition led to the stabilization and upregulation of TIPE2 protein expression, accompanied by a significant reduction in the levels of inflammatory mediators such as IL-1β and i NOS. Conclusion: Effective inhibition of the pivotal signaling kinase TAK1 markedly attenuates ubiquitin-mediated degradation of TIPE2 protein. Ubiquitination serves as a critical post-translational modification that targets proteins for proteasomal breakdown. Suppression of this degradative pathway leads to the accumulation and upregulation of TIPE2 expression. Consequently, elevated TIPE2 levels enhance its structural stability and functional availability, thereby potentiating its role as a negative immune regulator. This molecular cascade ultimately contributes to the amelioration of neuroinflammatory responses, revealing a promising therapeutic strategy for neuroprotection in neurological disorders. Targeting this mechanism may not only alleviate neuroinflammation in patients but also offer novel conceptual and translational avenues for the treatment and prevention of neurological diseases.

关键词

neuroinflammation / TIPE2 / TAK1 inhibitors / neuroimmunology