Low molecular mass chondroitin sulfate suppresses chronic unpredictable mild stress-induced depression-like behavior in mice

H2S-mediated aerobic exercise antagonizes the hippocampal inflammatory response in CUMS-depressed mice

PURPOSE

This thesis was to investigate the protective effect and mechanism of H₂S-mediated aerobic exercise on the antagonism of the hippocampus inflammatory response in CUMS-depressed mice.

METHOD

Seventy C57BL/6 mice were randomly divided into control group (CG), model control group (MG), model exercise group (ME), H₂S enhanced group (HG) and H₂S enhanced and exercise group (HE). All mice except CG underwent a 28-day CUMS depression model. ME and HE received moderate-intensity aerobic treadmill training for 8 weeks. They were randomly selected for Nissl staining, Immunofluorescence, methylene blue colorimetric assay, and ELISA. The levels of IL-10 and TNF-ɑ were detected by qRT-PCR, and the expression levels of CBS and inflammatory-related factors in the hippocampus were detected.

RESULT

Compared with CG, the number of erections, modifications, and crossing grids in MG mice were significantly reduced, the time of forced swimming and forced tail suspension was significantly prolonged, the positive rate of 5-HT decreased, and the symptoms of depression were obvious. The positive rate of CD45⁺ increased, the inflammatory response was obvious, and the content of H₂S and the expression of biosynthetic enzyme CBS decreased. Aerobic exercise and H₂S-enhanced mice improved depressive symptoms, decreased proinflammatory factors, increased anti-inflammatory factors, increased H₂S content, increased CBS expression, and increased H₂S.

CONCLUSION

H₂S may participate in aerobic exercise to antagonize the inflammatory process of the hippocampus in CUMS-depressed mice by reducing the release of inflammatory response factors and hippocampus nerve injury factors, and effectively alleviate inflammatory injury in the hippocampus of depressed mice.

Isoflurane produces antidepressant effects inducing BDNF-TrkB signaling in CUMS mice

RATIONALE

The volatile anesthetic isoflurane is suggested to produce a rapid and robust antidepressive effect in preliminary clinical trials. Recently, isoflurane was found to activate the tropomyosin receptor kinase B (TrkB) signaling which is the underlying mechanism of the rapid antidepressant ketamine.

OBJECTIVE

Our study investigated the effect of isoflurane anesthesia on chronic unpredictable mild stressed (CUMS) model in mice and verified the role of brain-derived neurotrophic factor (BDNF)/TrkB/ the mammalian target of rapamycin (mTOR) signaling in the antidepressant effect of isoflurane.

METHODS

We employed the CUMS model of depression to assess the rapid antidepressant effect of isoflurane by the forced swimming test (FST), the sucrose preference test (SPT), and the novelty suppressed feeding test (NSFT). The protein expression of BDNF and TrkB/protein kinase B (PKB or Akt)/mTOR was determined through Western blot. The dendritic spine density in the hippocampus and medial prefrontal cortex (PFC) was measured by the Golgi staining.

RESULTS

A brief burst-suppressing isoflurane anesthesia rapidly reversed the behavioral deficits caused by CUMS procedure, normalized the expression of BDNF and further activated the TrkB signaling pathway in CUMS-induced stressed mice in both prefrontal cortex (PFC) and hippocampus (HC). All of those behavioral and proteomic effects were blocked by K252a, a selective receptor inhibitor of TrkB. Isoflurane significantly promoted the formation of dendritic spines in both medial prefrontal cortex (mPFC), CA1, CA3, and DG of the hippocampus.

CONCLUSION

Our study indicates that isoflurane exerts a rapid antidepressant-like effect in CUMS depression animal model, and the activation of BDNF/TrkB signaling pathway plays an indispensable role in the biological and behavioral antidepressant effects of isoflurane. A single exposure to isoflurane could repair synaptic damage caused by chronic stimulation.