Interleukin 17A Derived from γδ T Cell Induces Demyelination of the Brain in Angiostrongylus cantonensis Infection

IL-17A Mediates Demyelination by Activating A1 Astrocytes via SOCS3 During Angiostrongylus cantonensis Infection

Background

Demyelinating disease of the central nervous system is one of the most common neurological diseases and effective treatment is still under in-depth research. Our previous study showed that Angiostrongylus cantonensis infection can induce demyelination injury in mouse brains and IL-17A expression was shown to be significantly increased during this process. Moreover, we found that IL-17A inhibition attenuated the demyelination caused by A. cantonensis infection. However, the underlying mechanisms have not yet been fully elucidated.

Methods

IL-17A neutralizing antibodies were injected into A. cantonensis infected mice to decrease IL-17A levels. The activation of glial cells in the brain and the expression of cell markers were detected by a variety of methods, including real-time quantitative PCR, western blotting, and immunofluorescence staining. The relationship between IL-17A and astrocyte activation was further identified by in vitro experiments. The role of SOCS3 in the IL-17A stimulating process was determined using RNA-seq data collection of infected mice and the siRNA interference method.

Results

Demyelination of the corpus callosum was relieved after administration of IL-17A neutralizing antibody and this was accompanied by decreased activation of A1 type astrocytes around this region. The expression of SOCS3 was attenuated and activation of astrocytes by IL-17A was mediated by the IL-17RA/STAT3/SOCS3 pathway. IL-17A not only directly damaged oligodendrocytes but also indirectly damaged oligodendrocytes through A1 astrocyte mediation. Specific siRNA inhibition of IL-17A-inducible SOCS3 in astrocytes alleviated their damaging effects on oligodendrocytes.

Conclusion

IL-17A plays an important role in demyelination induced by A. cantonensis infection via the IL-17RA/STAT3/SOCS3 pathway in A1-type astrocytes, indicating that specific blockage of IL-17A and SOCS3 activity could be a therapeutic strategy for neuroinflammatory demyelinating diseases associated with astrocyte activation.

IL-17 signaling induces iNOS+ microglia activation in retinal vascular diseases

Activation of microglia and inflammation-mediated vascular damages are suggested to play a decisive role in the pathogenesis of various retinopathies. The inducible nitric oxide synthase (iNOS) was required for activated microglia-mediated injuries. However, the induction mechanism of microglia activation during retinal vascular diseases is still elusive. Here we showed that IL-17 induced microglia activation with high expression of iNOS and promoted the development of retinal vascular diseases. IL-17-dependent activation of the STAT3-iNOS pathway was essentially required for microglia activation, which promoted endothelial cell growth and accelerated vascular leakage and leukostasis via IL-6 in vitro and in vivo. Taken together, our data provide novel mechanistic insights on microglia activation-mediated retinopathy, unveil the specific role of IL-17 on microglia, and define novel therapeutic targets for treating retinal vascular diseases.