TLR4 inhibitor resatorvid provides neuroprotection in experimental traumatic brain injury: Implication in the treatment of human brain injury

• The expression of TLR4 and TAK1 was increased in human brain after acute injury.
• Resatorvid reduced neuronal apoptosis to protect brain from injury following TBI.
• Resatorvid reduced TAK1 expression.
• Resatorvid curtailed IL-1β and TNF-α expression after TBI.

Toll-like receptor 4 (TLR4) is considered to play an important role in neuronal death in animal models and could be an important therapeutic target following traumatic brain injury (TBI). Resatorvid is a small molecule, commonly accepted to inhibit TLR4-mediated pathway. The purpose of this study was to investigate the neuroprotective effect of resatorvid after TBI. Our data revealed that inhibition of TLR4 by resatorvid attenuated the development of TBI in mouse model. And we found that resatorvid administration dramatically reduced neuronal apoptosis. To investigate the cellular mechanism, we evaluated the expression of transforming growth factor-β-activated kinase 1 (TAK1), which plays a crucial role in TLR4 signal transduction pathway and is activated by phosphorylation in response to TBI. In addition, enzyme-linked immunosorbent assay was used to determine the expression of tumor necrosis factor-α (TNF-α) and interlukin-1β (IL-1β) at 24 h after injury. Our results showed that resatorvid treatment significantly reduced the protein levels of TAK1, p-TAK1, TNF-α, and IL-1β compared with vehicle treatment. Importantly, the delayed therapy (4 h post injury) once daily consecutively for 5 days ameliorated brain damage and improved neurological recovery, suggesting that this drug has a wide therapeutic time window. Clinically, we observed that TLR4 and TAK1 expression was significantly increased in human contusion specimens after TBI. These data provide an experimental rationale for the evaluation of TLR4 as a clinical target and therapeutic implication of resatorvid in human traumatic brain injury.