[Mechanism of Xiaoyao Kangai Jieyu Formula in improving hippocampal neurovascular unit damage in breast cancer-related depression via HMGB1/TLR4 signaling pathway].

This paper aims to investigate the potential mechanism of action of Xiaoyao Kangai Jieyu Formula in treating breast cancer-related depression(BCRD).Thirty-two BALB/c mice were randomly assigned to a BCRD group,a positive drug group,a TCM group,and a blank control group.Except for those in the blank control group,the mice in all other groups received axillary inoculation of 1×10~6 4T1 inflammatory breast cancer cells(abbreviated 4T1).After tumor formation,the corticosterone suspension was subcutaneously injected into the back for 21 days to replicate the BCRD model.Simultaneously,oral administration of the treatment was initiated at the start of corticosterone injections and continued for 21 days.Depressive-like behaviors of mice were observed using the novel food test,tail suspension test,and open field test.Tumor volume,tumor weight,and tumor inhibition rate were measured in axillary subcutaneous tumors of mice.Histopathological changes of the tumors were examined via HE staining.DHE staining was used to detect the hippocampal reactive oxygen species(ROS) levels;immunofluorescence triple labeling was employed to detect changes in marker proteins of various cells in the hippocampal neurovascular unit(NVU);Nissl staining was used to examine the morphology of Nissl bodies in hippocampal neurons;a transmission electron microscope was used to examine the ultrastructure in hippocampal NVU cells.qRT-PCR and Western blot were employed to detect gene and protein expressions of high-mobility group box 1(HMGB1),tolllike receptor 4(TLR4),interleukin-1β(IL-1β),and tumor necrosis factor-α(TNF-α) in the hippocampus.The results show that compared with those in the blank control group,the mice in the BCRD group exhibit significantly reduced total activity distance and total activity count in the open field(P<0.01),along with significantly increased tail suspension immobility time and first feeding time in the novel food test(P<0.05,P<0.01),indicating pronounced depressive-like behavior of mice in the BCRD group.ROS levels in the hippocampus were elevated.Significant increases in hippocampal HMGB1,TLR4,IL-1β,and TNF-α protein expression were observed(P<0.01).The marked damage to various cellular structures within the NVU was evident(P<0.05,P<0.01).Compared with the BCRD group,depressive behavior was significantly improved in mice in both the positive control drug group and the TCM group;in the positive control group,the expression of HMGB1,TLR4,and TNF-α proteins in the hippocampus decreased,and the expression of IL-1β protein was significantly reduced(P<0.05);in the TCM group,the expression of HMGB1,TLR4,IL-1β,and TNF-α proteins in the hippocampus was significantly reduced(P<0.05,P<0.01);cellular damage in the hippocampal NVU was alleviated.The positive drug group achieved a tumor inhibition rate of 32.43%,while the TCM group reached 44.59%,with both demonstrating slower tumor growth than the BCRD group.In conclusion,Xiaoyao Kangai Jieyu Formula may regulate the HMGB1/TLR4 signaling pathway by inhibiting oxidative stress,thereby improving hippocampal NVU damage and treating BCRD.