Objective:To investigate the relationship between NOD-like receptors 3 (NLRP3) inflammasomes mediated inflammatory response and the pathogenesis of depression, and to investigate the effect of fluoxetine on this process.Methods:120 male C57BL/6J (wild-type) mice were randomly divided into control group 1, control group 2, chronic unpredictable mild stress (CUMS) group, and CUMS plus fluoxetine group. Another 30 male C57BL/6J (NLRP3-/-) mice were selected as NLRP3-/- group. Control group 1 and control group 2 had No treatment; CUMS group, CUMS plus fluoxetine group, and NLRP3-/- group were given chronic unpredictable mild stimulation for six weeks. After modeling, mice in control group 2 and CUMS plus fluoxetine group were intraperitoneally injected with fluoxetine (10 mg/(kg·d)). In contrast, mice in the other three groups were injected with the same amount of normal saline every day for four weeks. Behavioral tests were performed once a week before and after stress stimulation. Tail venous blood was drawn immediately before stress stimulation, three weeks later and six weeks after stress stimulation and was centrifuged at 3000 r/min for 10 min. The supernatant was kept and frozen for future use. Serum levels of interleukin-1β(IL-1β) and interleukin-18 (IL-18) were detected by enzyme-linked immunosorbent assay. After drug intervention (10 mg/(kg·d) fluoxetine or the same volume of normal saline), the mice in each group underwent behavioral tests once a week. The results included the sugar water preference test, forced swimming test (FST), and tail suspension test (TST). Tail venous blood was drawn from mice in each group at 1, 3, and 4 weeks after fluoxetine administration, and the supernatant was centrifuged and stored for later use. Serum levels of IL-1β and IL-18 were detected by enzyme-linked immunosorbent assay. At the above time points, 5 mice in each group were sacrificed each time, and fresh hippocampal tissues were collected and stored at a low temperature. NLRP3, urinary winter peptidase (caspase-1), the induction of transcription factors-KB (nuclear factor-κB, NF-κB), IL-1β and the IL-18 in the hippocampus brain regions were detected by using Western Blot.Results:(1) Model establishment: After six weeks of CUMS, compared with control group 1 and control group 2, the sugar water consumption of mice in CUMS group and CUMS+fluoxetine group was significantly reduced, and the immobility time of FST and TST was significantly prolonged, which proved that the model establishment was successful. After CUMS, NLRP3-/- group mice did not show depression-like changes in FST, sugar water preference test, and TST, which indicated that the model failed to be established. (2) After intraperitoneal fluoxetine injection, there were no significant differences in sugar water consumption, FST and TST immobility time between control group 2 and control group 1 ( P>0.05), and the sugar water consumption of mice in CUMS plus fluoxetine group was significantly increased, compared with CUMS group ( P<0.05). The immobility time of FST and TST was significantly shortened ( P<0.05). (3) The results of the enzyme-linked immunosorbent assay showed that after stimulation of CUMS, compared with control group 1 and control group 2, the serum levels of IL-1β and IL-18 in CUMS group and CUMS plus fluoxetine group were significantly increased ( P<0.05), while NLRP3-/- group had no significant change ( P>0.05). After fluoxetine administration, the serum levels of IL-1β and IL-18 in CUMS plus fluoxetine group were significantly lower than those in CUMS group ( P<0.05). (4) Western blotting results showed that after stimulation of CUMS, compared with control group 1 and control group 2, mice brain hippocampus NLRP3 expression, caspase-1 activation and induction of transcription factors-κB (nuclear factor-κB, NF-κB), IL-1β, IL-18 expression significantly increased ( P<0.05) in CUMS and CUMS plus fluoxetine group. After fluoxetine treatment, mice brain hippocampus NLRP3 expression, caspase-1 activation, NF-κB, IL-1β, and IL-18 expression in CUMS plus fluoxetine group had a significant reduction (restored to control 1 group by 99%, 91%, 97%, 95%, and 97% respectively). Conclusion:(1) CUMS may bring more NLRP3, caspase-1, NF-κB, IL-1β, and IL-18 expression in mice hippocampus, which cannot be seen, in the NLRP3 gene knockout mice; (2) The fluoxetine treatment may significantly decrease the NLRP3, caspase-1, NF-κB, IL-1β, IL-18 expression on depressive model mice, and improve depressive behavior.

Objective:To investigate the relationship between NOD-like receptors 3 (NLRP3) inflammasomes mediated inflammatory response and the pathogenesis of depression, and to investigate the effect of fluoxetine on this process.Methods:120 male C57BL/6J (wild-type) mice were randomly divided into control group 1, control group 2, chronic unpredictable mild stress (CUMS) group, and CUMS plus fluoxetine group. Another 30 male C57BL/6J (NLRP3-/-) mice were selected as NLRP3-/- group. Control group 1 and control group 2 had No treatment; CUMS group, CUMS plus fluoxetine group, and NLRP3-/- group were given chronic unpredictable mild stimulation for six weeks. After modeling, mice in control group 2 and CUMS plus fluoxetine group were intraperitoneally injected with fluoxetine (10 mg/(kg·d)). In contrast, mice in the other three groups were injected with the same amount of normal saline every day for four weeks. Behavioral tests were performed once a week before and after stress stimulation. Tail venous blood was drawn immediately before stress stimulation, three weeks later and six weeks after stress stimulation and was centrifuged at 3000 r/min for 10 min. The supernatant was kept and frozen for future use. Serum levels of interleukin-1β(IL-1β) and interleukin-18 (IL-18) were detected by enzyme-linked immunosorbent assay. After drug intervention (10 mg/(kg·d) fluoxetine or the same volume of normal saline), the mice in each group underwent behavioral tests once a week. The results included the sugar water preference test, forced swimming test (FST), and tail suspension test (TST). Tail venous blood was drawn from mice in each group at 1, 3, and 4 weeks after fluoxetine administration, and the supernatant was centrifuged and stored for later use. Serum levels of IL-1β and IL-18 were detected by enzyme-linked immunosorbent assay. At the above time points, 5 mice in each group were sacrificed each time, and fresh hippocampal tissues were collected and stored at a low temperature. NLRP3, urinary winter peptidase (caspase-1), the induction of transcription factors-KB (nuclear factor-κB, NF-κB), IL-1β and the IL-18 in the hippocampus brain regions were detected by using Western Blot.Results:(1) Model establishment: After six weeks of CUMS, compared with control group 1 and control group 2, the sugar water consumption of mice in CUMS group and CUMS+fluoxetine group was significantly reduced, and the immobility time of FST and TST was significantly prolonged, which proved that the model establishment was successful. After CUMS, NLRP3-/- group mice did not show depression-like changes in FST, sugar water preference test, and TST, which indicated that the model failed to be established. (2) After intraperitoneal fluoxetine injection, there were no significant differences in sugar water consumption, FST and TST immobility time between control group 2 and control group 1 ( P>0.05), and the sugar water consumption of mice in CUMS plus fluoxetine group was significantly increased, compared with CUMS group ( P<0.05). The immobility time of FST and TST was significantly shortened ( P<0.05). (3) The results of the enzyme-linked immunosorbent assay showed that after stimulation of CUMS, compared with control group 1 and control group 2, the serum levels of IL-1β and IL-18 in CUMS group and CUMS plus fluoxetine group were significantly increased ( P<0.05), while NLRP3-/- group had no significant change ( P>0.05). After fluoxetine administration, the serum levels of IL-1β and IL-18 in CUMS plus fluoxetine group were significantly lower than those in CUMS group ( P<0.05). (4) Western blotting results showed that after stimulation of CUMS, compared with control group 1 and control group 2, mice brain hippocampus NLRP3 expression, caspase-1 activation and induction of transcription factors-κB (nuclear factor-κB, NF-κB), IL-1β, IL-18 expression significantly increased ( P<0.05) in CUMS and CUMS plus fluoxetine group. After fluoxetine treatment, mice brain hippocampus NLRP3 expression, caspase-1 activation, NF-κB, IL-1β, and IL-18 expression in CUMS plus fluoxetine group had a significant reduction (restored to control 1 group by 99%, 91%, 97%, 95%, and 97% respectively). Conclusion:(1) CUMS may bring more NLRP3, caspase-1, NF-κB, IL-1β, and IL-18 expression in mice hippocampus, which cannot be seen, in the NLRP3 gene knockout mice; (2) The fluoxetine treatment may significantly decrease the NLRP3, caspase-1, NF-κB, IL-1β, IL-18 expression on depressive model mice, and improve depressive behavior.