Attenuated Inflammatory Response in Triggering Receptor Expressed on Myeloid Cells 2 (TREM2) Knock-Out Mice following Stroke
Figure 1
Expression of TREM2 and pro-inflammatory cytokine transcripts in C57BL/6 and TREM2-KO mice after stroke.
A. Gene transcripts for TREM2 were determined at 6 h, 12 h, 24 h, 2 d, 7 d and 28 d after stroke in the ipsilateral ischemic hemisphere of C57BL/6 mice. TREM2 was up-regulated at 7 d and 28 d after stroke. Data are displayed as mean ± s.e.m. (ratio ipsi vs. contra), n = 4 each, ***p≤0.001. B. TREM2 gene transcripts were determined at 12 h, 7 d and 28 d after stroke (MCAO) as well as after sham procedure (Sham) in TREM2-KO mice (KO) and littermate controls (WT). Increased TREM2 gene transcription was detected in the ischemic hemisphere of littermate controls (WT MCAO ipsi) at 7 d and 28 d. No increased gene transcripts for TREM2 were observed after stroke in littermate controls at the contralateral side (WT MCAO contra) and following sham procedure (WT Sham). TREM2-KO mice (KO) did not show any TREM2 gene transcription. C. Gene transcripts of cytokines were determined after stroke (MCAO) as well as after sham procedure (Sham) in TREM2-KO mice (KO) and littermate controls (WT). A strong up-regulation of pro-inflammatory cytokines (TNFα, IL-1α, IL-1β and IL-6) was observed 12 h after stroke. A reduced gene transcription of TNFα, IL-1α and IL-1β was observed in TREM2-KO (KO MCAO ipsi) compared to littermate control mice (WT MCAO ipsi) at 7 d after stroke. No differences in cytokine gene transcription were revealed between TREM2-KO mice (KO MCAO ipsi) and littermate controls (WT MCAO ipsi) at 12 h and at 28 d. No increased cytokine expression was observed after stroke in littermate controls at the contralateral side (contra) and in sham operated mice (Sham). Bars represent mean ± s.e.m. (mRNA copies per 1,000 Gapdh), sham: n = 3 each and MCAO: n = 5/6 each, WT ipsi vs. WT contra #p≤0.05, ##p≤0.01, WT ipsi vs. KO ipsi *p≤0.05, **p≤0.01, ***p≤0.001.