ß-arrestin2 is indispensable for the antidepressant effects of fluoxetine via inhibiting astrocytic pyroptosis in chronic mild stress mouse model for depression.

ß-arrestin2 is a versatile protein for signaling transduction in brain physiology and pathology. Herein, we investigated the involvement of ß-arrestin2 in pharmacological effects of fluoxetine for depression. A chronic mild stress (CMS) model was established using wild-type (WT) and ß-arrestin2-/- mice. Behavioral results demonstrated that CMS mice showed increased immobility time in the tail suspension test and forced swimming test, elevated concentrations of pro-inflammatory factors in peripheral blood, increased expression of pyroptosis-related proteins, and increased co-labeling of glial fibrillary acidic protein and Caspase1 p10 in the hippocampus compared to the CON group. Treatment with fluoxetine (FLX) ameliorated these conditions. However, compared with the ß-arrestin2-/- CMS group, these results of the ß-arrestin2-/- CMS + FLX group showed no significant changes. These results suggested that the above effects of FLX could be eliminated by knocking out ß-arrestin2. Mass spectrometry implying that FLX promoted the binding of ß-arrestin2 to the NLRP2 inflammasome of depressed mice. Subsequently, the results of the cellular experiments suggested that the 5HT2B receptor antagonist may attenuate L-kynurenine + ATP-induced cell pyroptosis by attenuating NLRP2 binding to ß-arrestin2. We further found that the lack of ß-arrestin2 eliminated the anti-pyroptosis effect of fluoxetine. In conclusion, ß-arrestin2 is an essential protein for fluoxetine to alleviate pyroptosis in the hippocampal astrocytes of CMS mice. Mechanistically, we found that the 5-HT2BR-ß-arrestin2-NLRP2 axis is vital for maintaining the antidepressant effects of fluoxetine.

Designing the 5HT2BR structure and its modulation as a therapeutic target for repurposing approach in drug-resistant epilepsy.

The study intends to repurpose FDA drugs and investigate the mechanism of (5HT2BR) activation by comprehending inter-residue interactions. The 5HT2BR is a novel thread, and its role in reducing seizures in Dravet syndrome is emerging. The crystal structure (5HT2BR) is a chimera with mutations; hence 3D-structure is modeled (4IB4: 5HT2BRM). The structure is cross-validated to simulate the human receptor using enrichment analysis (ROC: 0.79) and SAVESv6.0. Virtual screening of 2456 approved drugs yielded the best hits that are subjected to MM/GBSA and molecular dynamic (MD) simulations. The 2 top drugs Cabergoline (-53.44 kcal/mol) and Methylergonovine (-40.42 kcal/mol), display strong binding affinity, and ADMET/SAR analysis also suggests their non-mutagenic or non-carcinogenic nature. Methylergonovine has a weaker binding affinity and lower potency than standards [Ergotamine (agonist) and Methysergide (antagonist)] due to its higher Ki (1.32 M) and Kd (6.44 ×10-8 M) values. Compared to standards, Cabergoline has moderate binding affinity and potency [Ki = 0.85 M and Kd = 5.53 × 10-8 M]. The top 2 drugs primarily interact with conserved residues (ASP135, LEU209, GLY221, ALA225, and THR140) as in agonists, unlike the antagonist. The top 2 drugs, upon binding to the 5HT2BRM, modify the helices VI, V, and III and shift the RMSD 2.48 Å and 3.07 Å. LEU209 forms a latch with residues 207-214 (forms a lid) in the 5HT2BRM receptor, which enhances agonist binding and prevents drug escape. Methylergonovine and Cabergoline interact more stongly with ALA225 than the antagonist. The post-MD analysis of Cabergoline suggests a better MM/GBSA value (-89.21 kcal/mol) than Methylergonovine (-63.54 kcal/mol). In this study, Cabergoline and Methylergonovine's agonistic mechanism and solid binding properties suggest their strong role in regulating the 5HT2BR and might target drug-resistant epilepsy.

Alpha-smooth muscle actin and serotonin receptors 2A and 2B in dogs with myxomatous mitral valve disease.

Canine Myxomatous mitral valve disease (MMVD) is an age-related disease. Serotonin (5-HT) is implicated in the pathogenesis as locally-produced or platelet-derived. Involvement of the 5-HT2A receptor (R) and 5-HT2BR in the induction of myxomatous-mediating valvular myofibroblasts (MF) has been suggested. In an age-matched population of dogs with non-clinical and clinical MMVD, the objectives were to investigate (1) gene expression of 5-HT2AR and 5-HT2BR, (2) protein expression and spatial relationship of 5-HT2AR, 5-HT2BR and MF in the mitral valve (MV) and the cardiac anterior papillary muscle (AP) and (3) serum 5-HT concentrations. Gene expression of 5-HT2BR was significantly higher in MV and AP among dogs with clinical MMVD. This was not found for 5-HT2BR protein expression, though association of 5-HT2BR with myxomatous pathology and co-localization of 5-HT2BR and MF in MV and AP support a functional relationship, perhaps perpetuation of clinical MMVD. 5-HT2AR-expression and serum 5-HT showed no differences between groups.