Seahorse Attenuated DSS-Induced Depression in Mice by Inhibiting Neuroinflammation and Ferroptosis

Abstract

Seahorse (Hippocampus abdominalis), a small fish, has been extensively utilized in traditional Chinese medicine to enhance and harmonize vital energy throughout the body and brain. This study aimed to elucidate the therapeutic role and underlying mechanism of seahorse in treating depressive symptoms. The therapeutic potential of seahorse was investigated in mice induced by dextran sulfate sodium (DSS) via behavioral tests, histopathological examinations, immunofluorescence staining, and transmission electron microscopy detection. Our findings revealed that seahorse effectively alleviated colitis symptoms by DSS, as shown by reduced inflammatory markers and enhanced expression of claudin-1 in the colonic tissues. More importantly, these gastrointestinal improvements were paralleled by significant attenuation of depressive behaviors, including improved anhedonia and reduced despair-like responses. Furthermore, seahorse exhibited a potent anti-inflammatory effect on brain tissues, evidenced by a decreased number of microglia in the hippocampal CA1 region, reduced expression of pNF-κB and NLRP3, and lowered cytokine levels. Additionally, seahorse promoted neurogenesis in the hippocampal DG region, enhanced brain-derived neurotrophic factor (BDNF) content in the CA1 region, and induced the pNrf2-mediated expression of HO-1, GPX4, and SLC7A11, collectively counteracting DSS-induced hippocampal ferroptosis. Transmission electron microscopy of mitochondria further confirmed that seahorse ameliorated DSS-induced mitochondrial atrophy and cristae deficiency. These results demonstrated that seahorse reversed IBD and comorbid depressive symptoms by regulating inflammation and ferroptosis. Our study highlights the multifaceted efficacy of seahorse in alleviating IBD and comorbid depressive symptoms, potentially offering a novel therapeutic avenue for these conditions.

Keywords: depression; ferroptosis; neuroinflammation; seahorse.

FIGURE 1

HPLC profile of seahorse at 254 nm, 17 peaks were elucidated: 1: Aspartic acid; 2: Glutamate; 3: Hydroxyproline; 4: Serine; 5: Glycine; 6: Histidine; 7: Arginine; 8: Threonine; 9: Alanine; 10: Proline; 11: Tyrosine; 12: Valine; 13: Methionine; 14: Isoleucine; 15: Leucine; 16: Phenylalanine; 17: Lysine.

FIGURE 2

Effects of seahorse in ameliorating colitis and depression symptoms in DSS‐induced mice (n = 10). (A) Schematic representation of the experimental design. (B) Changes in body weight. (C) DAI scores. (D) Colon length. (E) Representative histological images of colon sections from each group stained with H&E; pathology scores (right panel) were evaluated using the criteria in Table 2: severity of inflammation (0–4), degree of damage (0–4), crypt damage (0–4), and percentage of affected area (0–4). Scale bars represent 200 μm. (F) Sucrose preference. (G) Immobility time. #p < 0.05 and ##p < 0.01 vs. control group; *p < 0.05 and **p < 0.01 vs. DSS‐induced model group.

FIGURE 3

Seahorse alleviated the impaired tight junction protein claudin‐1 in DSS‐induced mice (n = 8). (A) Immunofluorescence staining for claudin‐1 in colonic sections of mice. (B) The histogram of claudin‐1 relative intensity. Scale bars represent 200 μm. #p < 0.05 vs. control group; *p < 0.05 and **p < 0.01 vs. DSS‐induced model group.

FIGURE 4

Effect of seahorses on DSS‐induced inflammation in mouse colon tissue (n = 8). (A) Immunofluorescence staining for NLRP3 in colonic sections of mice. (B) Immunofluorescence staining for NF‐κB p65 in colonic sections. Scale bars are set at 200 μm. #p < 0.05 and ##p < 0.01 vs. control group; *p < 0.05 and **p < 0.01 vs. DSS‐induced model group.

FIGURE 5

Effect of seahorses on DSS‐induced neuroinflammation in the hippocampal CA1 region (n = 6). (A) Quantitative and morphological analysis of microglia in the whole hippocampus of the mouse hippocampus. (B) Immunofluorescence staining for NLRP3. (C) Immunofluorescence staining for TLR4. (D) Immunofluorescence staining for phosphorylated NF‐κB. Immunofluorescence staining for proinflammatory cytokines (E) IL‐1β, (F) IL‐6, and (G) TNF‐α. Scale bar = 200 μm. #p < 0.05 and ##p < 0.01 vs. control group; *p < 0.05 and **p < 0.01 vs. DSS‐induced model group.

FIGURE 6

Effect of seahorses on the hippocampal neurotrophic function in hippocampal DG and CA1 region (n = 6). (A) Immunofluorescence staining for DCX in the DG region. (B) Immunofluorescence staining for NeuN in the DG region of the hippocampus. (C) Immunofluorescence staining for BDNF in the CA1 region. Scale bar = 200 μm. #p < 0.05 and ##p < 0.01 vs. control group; *p < 0.05 and **p < 0.01 vs. DSS‐induced model group.

FIGURE 7

Effect of seahorses on DSS‐induced ferroptosis in hippocampal CA1 region (n = 4). (A) Immunofluorescence staining for pNrf2 in the CA1 region. (B) Immunofluorescence staining for HO‐1 in the CA1 region. (C) Immunofluorescence staining for GPX4 in the CA1 region. (D) Immunofluorescence staining for SLC7A11 in the CA1 region. Scale bar = 200 μm. #p < 0.05 and ##p < 0.01 vs. control group; *p < 0.05 and **p < 0.01 vs. DSS‐induced model group.

FIGURE 8

Effect of seahorses on the cellular ultrastructure of DSS‐induced mouse hippocampal CA1 neurons (n = 4). (A) TEM images showing ultrastructural alterations in hippocampal mitochondria of mice. This panel highlights mitochondrial damage associated with DSS‐induced stress. Scale bar = 2 μm. (B) TEM analysis depicting the density and size of mitochondria surrounding the nuclei in the hippocampal region. These images provide quantitative insights into mitochondrial health and morphology. Scale bars = 2 μm (overview) and 1 μm (enlarged view). (C) Detailed TEM images of synaptic morphology within the mouse hippocampus, illustrating the structural integrity of synapses. Scale bar = 1 μm. (D) The histogram of mitochondria number. (E) The histogram of mitochondrial size. (F) The histogram of PSD length. (G) The histogram of PSD thickness. (H) The histogram of width of synaptic cleft. (I) Immunofluorescence staining for AIF in the CA1 region of the mouse hippocampus, indicating the extent of ferroptosis‐induced neuronal apoptosis. Scale bar = 200 μm. Statistical significance is denoted as follows: #p < 0.05 and ##p < 0.01 when compared to the control group; *p < 0.05 and **p < 0.01 in comparison to the DSS‐induced model group.