Ozone causes depressive-like response through PI3K/Akt/GSK3ß pathway modulating synaptic plasticity in young rats.

Ozone pollution has been associated with several adverse effects, including memory impairment, intellectual retardation, emotional disturbances. However, the potential mechanisms remain uncertain. The present study aimed to investigate whether ozone (O3) regulates synaptic plasticity through PI3K/Akt/GSK3ß signaling pathway and induces neurobehavioral modifications among the young rats. In vivo, the newborn rats were used to construct the animal model of early postnatal O3 treatment. In vitro, this study measured the effect of different concentrations of serum from O3 treated rats on the viability of the PC12 cells, and investigated the modifications of synaptic plasticity and PI3K/Akt/GSK3ß signaling pathway in the hippocampus and PC12 cells after O3 treated. The results revealed significant depression-like behavior and increased hippocampal histopathological damage in the young rats after O3 treated. Compared with the control group, the expression levels of synaptic related proteins including Drebrin, PSD95, Synaptophysin and PIK3R1, p-Akt, and p-GSK3ß were decreased in the O3 treated group. In vitro assays, a significant reduction in Drebrin, PSD95, Synaptophysin, PIK3R1, p-Akt, and p-GSK3ß was found in PC12 cells after O3 serum treated. While 740Y-P (a specific PI3K activator) administered, the expression levels of Drebrin, PSD95, Synaptophysin, PIK3R1, p-Akt, and p-GSK3ß in the 740Y-P + O3 group were significantly elevated in vivo and vitro compared with the O3-only group. In addition, miRNAs modulating PIK3R1 were screened on bioinformatics website, the study found aberrant expression of miR-221-3p in the hippocampus and serum of O3 treated group. Inhibition of miR-221-3p expression effectively reversed the reduction of Drebrin, PSD95, Synaptophysin, PIK3R1, p-Akt, and p-GSK3ß in PC12 cells induced by O3 treatment. Altogether, these studies indicate that O3 restrained the expression of PI3K/Akt/GSK3ß signaling pathway and impaired synaptic plasticity that resulted in depressive-like behavior in young rats. Moreover, miR-221-3p plays an important role in this procedure by regulating PIK3R1.

JAK2/STAT3 pathway regulates microglia polarization involved in hippocampal inflammatory damage due to acute paraquat exposure.

OBJECTIVE: To explore the effects of acute paraquat (PQ) exposure on the phenotypic polarization of hippocampal microglia and its mechanism. METHODS: An acute PQ exposure rat model was established. Male SD rats were exposed to 0, 5, 25, and 50 mg/kg PQ, and brain hippocampal tissue was collected after 1, 3, and 7 days of exposure, respectively. Hippocampal pathological changes were examined by H&E staining, and immunohistochemistry (IHC) was used to detect changes in the number of Iba-1-positive cells, the average number of endpoints, and the average process length. The protein expression of Iba-1 was detected by western blotting. BV-2 microglia were treated with 0, 0.01, 0.025, 0.05, or 0.1 µmol/L PQ for 24 h. ELISA and western blotting assays were performed to detect the expression of TNF-α and IL-1ß in vivo and in vitro. The M1 microglia marker iNOS, the M2 microglia marker Arg-1, and the p-JAK2 and p-STAT3 protein were detected by western blotting. JAK2/STAT3 pathway activation role in regulating microglia phenotypic polarization was further validated in vivo and in vitro by JAK2-specific inhibitor AG490 administration. RESULTS: After acute PQ exposure, hippocampal neurons showed pathological changes such as loose arrangement and nuclear pyknosis, the number of Iba-1 positive cells and the expression of Iba-1 protein increased, and the average number of endpoints and average process length of microglia decreased. Histological examination revealed that compared with the control group, in the 50 mg/kg PQ group on the 3rd and 7th day, the expression of TNF-α, IL-1ß, and iNOS significantly increased, while that of Arg-1 significantly decreased. p-JAK2 and p-STAT3 expression significantly increased in the 50 mg/kg PQ group on the 1st, 3rd, and 7th day. In vitro, compared with the control group, the expression of TNF-α, IL-1ß, iNOS, p-JAK2, and p-STAT3 significantly increased, while Arg-1 expression was significantly reduced in the 0.025, 0.05, and 0.1 µmol/L PQ groups. After AG490 administration, the expression levels of p-JAK2, p-STAT3, iNOS, TNF-α, and IL-1ß in the AG490 +PQ group were significantly inhibited in vivo and in vitro compared with the PQ-only group. On the contrary, Arg-1 expression was significantly increased. CONCLUSION: Our results suggest that acute PQ exposure may induce M1-type polarization of hippocampal microglia by activating the JAK2/STAT3 pathway, which in turn releases pro-inflammatory factors such as TNF-α and IL-1ß, leading to hippocampal inflammatory damage.

Elucidating the mechanisms underlying astrocyte-microglia crosstalk in hippocampal neuroinflammation induced by acute diquat exposure.

The transition from paraquat (PQ) to diquat (DQ), both organic dication herbicides, in China has led to significant increases in the number of acute DQ poisoning cases. Case studies have shown that acute DQ poisoning resulted in injury to the central nervous system (CNS), but the mechanism underlying the injury remains to be explored. The present study aimed to investigate how DQ influenced purinergic signaling between astrocytes and microglia and whether extracellular ATP (eATP) was involved in promoting neuroinflammation induced by acute DQ toxicity through the activation of the P2X4/NLRP3 signaling pathway. We constructed a rat model of acute DQ toxicity to observe the pathological changes in hippocampal tissues after DQ exposure and measure the expression levels of IL-1ß and TNF-α in the hippocampal tissue. We also established an in vitro co-culture model of C6 astrocytes and BV-2 microglia using transwell chambers, measured the amount of eATP secreted into C6 astrocytes after DQ treatment, and assessed the inflammatory response and changes in the P2X4/NLRP3 signaling pathway in BV-2 microglia. The results showed that the neurons in the hippocampal tissue of rats exhibited loose arrangement, nuclear consolidation, and necrosis after DQ exposure, and IL-1ß and TNF-α levels were signification higher in the hippocampal tissue after DQ exposure. DQ exposure to the co-cultured cells induced an increase in ATP secretion from C6 astrocytes as well as a significant increase of P2X4, NLRP3, IL-1ß, and IL-18 expression in BV-2 microglia. In contrast, pretreatment of C6 astrocytes with apyrase (an ATP hydrolase) resulted in a significant decrease of P2X4, NLRP3, IL-1ß, and IL-18 expression in BV-2 microglia. Furthermore, inhibition of P2X4 expression in BV-2 microglia by transfection with si-P2X4 effectively reversed the increase of NLRP3, IL-1ß, and IL-18 in BV-2 microglia induced by DQ when co-cultured with C6 astrocytes. These results indicate that astrocytes can activate the P2X4/NLRP3 signaling pathway in microglia through the DQ-induced extracellular release of ATP to promote neuroinflammation in rat hippocampal tissue.