Fig 1: Cystine prevented SI-induced spatial cognitive deficits through suppressed C-C motif chemokine ligand 7 (CCL7) expression in hippocampal microglia.a Experimental schedule of cystine treatment (100 mg/kg, p.o.). b The novel object location test (NOLT) following cystine treatment in GH and SI mice. Exploratory preference to object at novel location in the test session (right) was measured 24 h following the training session (left). Two-way ANOVA followed by Tukey’s multiple comparison test, Training session (SI [p = 0.3773], cystine [p = 0.6113], and SI ×cystine [p = 0.7262]); Test session (SI [**p < 0.01], cystine [**p < 0.01], and SI ×cystine [**p < 0.01]); n = 9–12 mice in each group. c Representative images of staining with anti-Iba1 (red) and Hoechst (blue) in the dentate gyrus (DG) of the hippocampus (HIP). Scale bar: 100 μm. d The number of Iba-1-positive cells was quantified in the DG of HIP (two-way ANOVA followed by Tukey’s multiple comparison test, SI [**p < 0.01], cystine [**p < 0.01], and SI ×cystine [**p < 0.01]; n = 4 mice in each group). e Schematic representation of the isolation of microglial nuclei from the HIP by cell sorter. f Representative flow cytometric plots of Pu.1+NeuN- cells in the HIP. g Percentage of Pu.1+NeuN- cells (two-way ANOVA followed by Tukey’s multiple comparison test, SI [**p < 0.01], cystine [**p < 0.01], and SI ×cystine [**p < 0.01]; n = 3 mice in each group). h Heat map of altered inflammatory cytokines and their receptors in the hippocampal microglia analyzed using qPCR arrays. The blue and red indicate lower and higher expression levels, respectively. Experimental schedule (i) and schema (j) of microinjections of CC motif chemokine receptor (CCR) 2 or 3 antagonists (20 nmol) into the HIP. k NOLT following microinjections of CCR2 or 3 antagonists. Exploratory preference to object at the novel location in the test session (right) was measured 24 h following the training session (left). Training session (Student’s t test, p = 0.943 vs. GH; one-way ANOVA followed by Tukey’s multiple comparison test, antagonists [p = 0.6753]); Test session (Student’s t test, ##p < 0.01 vs. GH; one-way ANOVA followed by Tukey’s multiple comparison test antagonists [**p < 0.01]; n = 8–10 mice in each group). Experimental schedule (l) and schematic representation (m) of microinjections of Clo-lip (7 mg/mL) and CCL7 (60 ng/µL) into the HIP. n Representative images of staining with anti-Iba1 (red) and Hoechst (blue) in the DG of HIP. Scale bar: 100 μm. o The NOLT following microinjections of Clo-lip and CCL7. Exploratory preference to object at the novel location in the test session (right) was measured 24 h following the training session (left). Training session (Student’s t test, p = 0.6500 vs. vehicle; p = 0.2169 vs. Clo-lip); Test session (Student’s t test, **p < 0.01 vs. vehicle; ##p < 0.01 vs. Clo-lip; n = 5–8 mice in each group). Data are expressed as mean ± SEM.