The ALK inhibitor lorlatinib attenuates lipopolysaccharide-induced neuroinflammation by inhibiting microglial activation and preserving blood–brain barrier integrity

Neuroinflammation plays a critical role in neurodegenerative diseases. Emerging evidence suggests that anaplastic lymphoma kinase (ALK) plays a pivotal role in the regulation of inflammation and innate immune signaling. However, the role of ALK in neuroinflammation has not been fully elucidated. To investigate the involvement of ALK in neuroinflammation, the present study examined the effects of the ALK inhibitor lorlatinib (LOR) on microglial activation and inflammatory responses in lipopolysaccharide (LPS)-stimulated BV2 microglial cells and the brains of LPS-injected mice. LOR suppressed nitric oxide and pro-inflammatory cytokine production while also inhibiting ALK phosphorylation in BV2 microglia. Similar anti-inflammatory effects were observed following ALK knockdown and treatment with another ALK inhibitor, ceritinib (CER), thereby supporting the involvement of ALK-dependent mechanisms. Mechanistically, LOR attenuated ALK-stimulator of interferon genes (STING) signaling and reduced the activation of interferon regulatory factor 3 (IRF3) and nuclear factor-κB (NF-κB), leading to decreased expression of type I interferons (IFNs) and inflammatory cytokines. It also reduced intracellular reactive oxygen species (ROS) levels and enhanced nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated antioxidant responses. In vivo, LOR administration inhibited microglial activation and reduced the expression of inflammatory mediators in the brains of LPS-injected mice. In addition, LOR preserved blood-brain barrier (BBB) integrity, as indicated by reduced Evans blue extravasation, immunoglobulin G (IgG) leakage, and restoration of tight junction (TJ) proteins. Overall, these findings identify ALK-STING signaling as a key regulator of neuroinflammation and suggest that LOR may represent a potential therapeutic agent for neuroinflammatory and neurodegenerative diseases.