Haibin Dai

The blood-brain barrier (BBB) is a layer between the blood circulation and neural tissue. It plays a pivotal role in maintaining the vulnerable extracellular microenvironment in the neuronal parenchyma. Neuroinflammatory events can result in BBB dysregulation by disturbing adherens junctions (AJs) and tight junctions (TJs). VE-cadherin, as one of the most important components of the vascular system, is specifically responsible for the assembly of AJs and BBB architecture. Here, we present a review, which highlights recently available insights into the relationship between the neuroinflammation and BBB dysregulation. We then explore the specific interaction between VE-cadherin and BBB. Finally, we discuss the changes of VE-cadherin with different neurological diseases from both experimental and clinical studies. An understanding of VE-cadherin in BBB regulation may indicate that VE-cadherin can partially be a biomarker of neuroinflammation disease and lead to novel approaches for abating BBB dysregulation under pathological conditions and the opening of the BBB following central nervous system (CNS) drug delivery.

Subarachnoid hemorrhage (SAH) elicits destruction of neuronal cells and neurological function, which is exacerbated by neuro-inflammation in EBI, and toll-like receptor 4 (TLR4) plays an important role in inflammatory cascade via modulation microglia polarization. Curcumin (Cur), as a natural phytochemical compound, has the potential characteristics on anti-inflammatory and microglia phenotype transformation. In this study, we verified the hypothesis curcumin promotes M2 polarization to inhibiting neuro-inflammation, which through suppressing TLR4 signaling pathway after SAH. In tlr4-/- mice and wild type (WT) subjected to prechiasmatic cistern blood injection, Western blotting, brain water content, neurological score, enzyme-linked immunosorbent assay (ELISA) and terminal deoxynucleotidyl transferase dUTP nick endlabeling (TUNEL) staining were performed to investigate the role of TLR4 on neuro-inflammation response and microglia polarization. Curcumin with three different concentrations (50 mg/kg, 100 mg/kg and 200 mg/kg) were injected intraperitoneally (i.p.) at 15 min after SAH. The levels of TLR4, myeloid differentiation factor 88 (MyD88), nuclear factor- κB (NF-κB), Iba-1, CD86, CD206 and pro/anti-inflammation cytokines were measured by Western blotting and immunofluorescence staining at 24 h after SAH. SAH induction increased the protein levels of TLR4, pro-inflammation cytokines and proportion of M1 phenotype. Curcumin with 100 mg/kg treatment dramatically inhibited the release of pro-inflammatory mediators, and elevated the protein levels of anti-inflammatory cytokines and promoted microglia switch to M2. Meanwhile, curcumin treatment also decreased the expressions of TLR4, Myd88 and NF-κB at 24 h post SAH. TLR4 deficiency ameliorated brain water content, neurological deficit and reduced pro-inflammation cytokines after SAH. Moreover, curcumin treatment in tlr4-/- mice further induced M2 polarization, while had no statistic difference on brain water content and neurological score at 24 h post SAH. Our results indicated that curcumin treatment alleviated neuro-inflammation response through promoting microglia phenotype shift toward M2, and which might inhibiting TLR4/MyD88/NF-κB signaling pathway after SAH.

Inflammation plays a key role in the progression of subarachnoid hemorrhage (SAH). Here, we examined the effects of astaxanthin (ATX) on the inflammatory response and secondary damage after SAH and the underlying mechanisms of action. In vivo, a prechiasmatic cistern injection model was established in rats and mice. In addition, neuron-microglia cocultures were exposed to oxyhemoglobin to mimic SAH in vitro. Western blotting revealed that protein expression of TLR4 was markedly increased in microglia at 24 h after SAH, with consequent increases in the downstream molecules myeloid differentiation factor 88 and NF-кB. Treatment with ATX significantly inhibited the TLR4 activation, increased sirtuin 1 expression, and inhibited the subsequent inflammatory response both in vivo and in vitro. ATX also significantly decreased high-mobility group box 1 nuclear translocation and secretion in neurons, an effect that was reversed by the sirtuin 1-specific inhibitor sirtinol. ATX administered 4 h after SAH ameliorated cerebral inflammation, brain edema, and neuronal death and improved neurologic function. ATX reduced neuronal death but did not improve neurologic function in TLR4 knockout mice. These results suggest that ATX reduces the proinflammatory response and secondary brain injury after SAH, primarily by increasing sirtuin 1 levels and inhibiting the TLR4 signaling pathway.-Zhang, X., Lu, Y., Wu, Q., Dai, H., Li, W., Lv, S., Zhou, X., Zhang, X., Hang, C., Wang, J. Astaxanthin mitigates subarachnoid hemorrhage injury primarily by increasing sirtuin 1 and inhibiting the Toll-like receptor 4 signaling pathway.