Interleukin 17 (IL-17) and its main producer,
T cell receptor γδ cells, have neurotoxic effects in the pathogenesis of
intracerebral hemorrhage (ICH), aggravating
brain injuries. To investigate the correlation between
IL-17 and ICH, we dynamically screened serum
IL-17 concentrations using
enzyme-linked
immunosorbent assay and explored the clinical values of
IL-17 in ICH patients. There was a significant negative correlation between serum
IL-17 level and neurological recovery status in ICH patients (r = -0.498, P < 0.01). To study the neurotoxic role of
IL-17, C57BL/6 mice were used to establish an ICH model by injecting autologous blood into the caudate nucleus. Subsequently, the mice were treated with mouse neural stem cells (NSCs) and/or
IL-17 neutralizing antibody for 72 hours. Flow cytometry, brain water content detection, Nissl staining, and
terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling results indicated that NSC
transplantation significantly reduced
IL-17 expression in peri-
hematoma tissue, but there was no difference in
T cell receptor γδ cells. Compared with the ICH group, there were fewer apoptotic bodies and more Nissl bodies in the ICH + NSC group and the ICH + NSC +
IL-17 group. To investigate the potential effect of
IL-17 on directional differentiation of NSCs, we cultured mouse NSCs (NE-4C) alone or co-cultured them with
T cell receptor γδ cells, which were isolated from mouse peripheral blood mononuclear cells, for 7 days. The results of western blot assays revealed that
IL-17 secreted by
T cell receptor γδ cells reduced the differentiation of NSCs into astrocytes and neurons, while
IL-17 neutralization relieved the inhibition of directional differentiation into astrocytes rather than neurons. In conclusion, serum
IL-17 levels were elevated in the early stage of ICH and were negatively correlated with outcome in ICH patients. Animal experiments and cytological investigations therefore demonstrated that
IL-17 probably has neurotoxic roles in ICH because of its inhibitory effects on the directional differentiation of NSCs. The application of
IL-17 neutralizing antibody may promote the directional differentiation of NSCs into astrocytes. This study was approved by the Clinical Research Ethics Committee of Anhui Medical University of China (For human study: Approval No. 20170135) in December 2016. All animal handling and experimentation were reviewed and approved by the Institutional Animal Care and Use Committee of Anhui Medical University (approval No. 20180248) in December 2017.